The first step in putting a mould together involves only the ribs and the four pieces of the frame. Other parts; a brass brace rod and extra ribs called waterbars will follow.
You may recall that one edge of each frame piece was intentionally left rough. This bottom edge is now smoothed by a single pass over the jointer.
Compressing the pegs by twisting them into a sized hole smooths out the facets left from the twelve sided rib peg tool. This also makes the ribs easier to fit into the holes in the sides of the mould.
Ribs are lightly sanded mainly to remove the little bits of wood that are left from drilling all the sewing holes.
The inside surfaces of the frame are also lightly sanded.
One end of each rib is inserted into a hole.
The penciled numbers are used to keep the ribs in the proper order.
Four ribs to go.
After all of the ribs are fitted in one side the whole assembly is carefully turned around so the free ends can be started into holes on the second side. One at a time, ribs are gently twisted back and forth while pushing them down. All will end up about halfway into the holes at each end. In this photo only the first and last rib (not visible here) have been moved down.
This just shows how the ribs move down as they are re-positioned. Three ribs have been moved down partway into the holes of the opposite frame piece.
When this step is completed the mould looks like this. The rib pegs are all about halfway into their holes.
Now the frame must be pushed in from both sides. This is done gradually as the sides are gently tapped together in small steps. Care is taken to tap evenly across the length of the frame, keeping the sides parallel. I turn the mould around each time so the sides get tapped from both sides equally.
After each stage of tapping all of the ribs are turned a bit in their holes. This is easy but important. Here the top five ribs have been ‘flipped’ down a little by my thumbs running down the sides. If the mould is assembled without doing this the ribs can become locked in; turned at odd angles. It can become difficult to straighten them and there is even a chance of breaking a rib.
When the pegs are all the way in their ends will be flush with the outside of the mould. Now they are aligned with the scribed marks on top. Both ends are rotated at the same time to make a rib stand nearly straight up; then each end can be individually nudged into position.
The narrow top surfaces should be centered on the scribed lines.
Now the ribs are completely inserted and aligned.
The holes drilled to receive the brass brace rod now line up perfectly.
The ends of the mould can be fitted in place.
The mould frame should be square, or very nearly so. This is the cumulative result of the care taken to make all of the pieces, ribs and frame, as straight as possible, with ends cut perfectly square; and of being certain to drill the rib peg holes into the frame at exactly 90 degrees.
This batch turned out very well!
Five assembled moulds, ready to be fitted with brace rods and waterbars.
The ribs have been shaped, cut to length and have had pegs formed on their ends. Now each must be drilled for a brace rod and then for sewing holes. The brace rod keeps the ribs lined up and helps them work together for added strength. A row of very small evenly spaced sewing holes are made along the thin upper edge of each rib. These sewing holes must be drilled ahead before a mould is assembled. Later, a single sewing wire will follow a spiral path through all the holes in each rib. Between each pair of sewing holes it will pass up and over the chain wires to attach the wire facing to the mould.
The ribs are all marked on one end. While they are being drilled and later assembled in the mould they must be kept in this orientation with (in this case) the mark always being on the right.
Skipping ahead a few steps shows why this is important. Using care to orient the ribs and holding them against fixed stops while drilling insures that the brace holes line up. In this photo the holes are already there; the drill is the best way I’ve found to insert the brass brace rod.
This base has slanted faces so the ribs will stand up straight in the mould after assembly. At the top of the slanted surface is an edge that the ribs are pushed up against; a ‘fence’ that spaces the hole a precise distance from the top edge of the rib.
A stop is fixed at the left to push the ribs against while an 1/8″ brace hole is drilled in the middle of each. Larger moulds often have two brace rods.
Each rib is held in place on the slanted surface of the base and against the stop while a clean hole is made with a brad point drill.
Another view of the drilling set-up.
Ribs for a mould. A few still need to be drilled for the brace rod.
Sewing holes are drilled next.
A #60 twist drill is used. The largest wire that I use for sewing is .013″ diameter (for sewing down wove backing) and these .040″ diameter (1mm) holes have proved to be plenty large.
The ribs are given an identical cluster of three holes at both ends. Stitches at the ends of the ribs will be closely spaced; a stitch every other space followed by one each for the last three spaces.
Holes drilled in the ribs of this laid mould have regulated the spacing of the stitches. Along a rib stitches fall between every pair of sewing holes, crossing over a pair of chain wires and between a pair of laid wires. From rib to rib the stitches are staggered so they won’t line up along the laid wires. Both features are pre-determined by the way the holes were drilled in the ribs before assembly. If you look closely you can see where the sewing wires pass through the holes in the ribs, about halfway between stitches.
I space the sewing holes for laid moulds at a stitch for every six laid wires. A serrated ‘rack’ is made for each configuration of laid facing. Above, preparing to cut teeth on a strip of inexpensive, easy to work Sintra plastic. To get the proper spacing a completed laid facing is laid on top and marks are drawn by pushing the pen point down between the wires, every sixth space.
Notches are cut on the tablesaw with the hollow ground blade.
One side of each notch is chiseled away to make teeth, like saw teeth. Once it is finished a strip can be used to make any number of laid moulds that share the same wire spacing.
The serrated strip is clamped on top of the base block. A little block (a ‘pawl’) fits over the rib peg to engage the strip. The pawl has a slanted face that clicks in and out of the spaces between the teeth. The rib can be rapidly re-positioned, moving from left to right as sewing holes are drilled at the proper spacing. Holes should be close to the top edge of the ribs so the sewing wire won’t need to be excessively long.
The holes must not be made in the same position on all of the ribs. If stitches pass between the same two laid wires on adjacent ribs it can create a depressed channel in the wires that may show in the paper. This drawing shows a system that helps the stitches skip around without creating an obvious pattern. This random-seeming pattern repeats and every fourth rib is drilled the same.
This laid mould has 14 ribs. I have separated them into four piles and numbered them #1,#2,#3 and #4. All ribs in each pile are drilled the same according to the pattern.
To do this, I drill a test rib (using the pawl and serrated fence) and label it #1. Lines are drawn to divide the spaces between holes into sixths. Each of the #1 ribs is now drilled using this first set-up, creating a row of evenly spaced holes along its entire length . (I’m making four moulds with the same laid wire spacing so all of the #1 ribs for all of these moulds are drilled at the same time, in this case about 16 ribs). Before drilling the #2 ribs the serrated strip is shifted slightly. Using this test rib as a gauge the drill will be set at the mark indicated by the #2 arrow, two increments to the left of the #1 hole. Then all the #2 ribs are drilled, each along its full length between the three-hole cluster at each end. Still following the pattern shown in the drawing the serrated strip is shifted three spaces to the right before drilling all of the #3 ribs. Finally, the strip is shifted two more spaces to the right before drilling the #4 ribs. I don’t know if mould makers would have done this in the past. Perhaps they would just drill (or pierce) the sewing holes by eye to an approximate spacing.
Many old moulds show evidence that the sewing holes were pierced rather than drilled. This may have been done with a device which was squeezed by hand to push a steel pin with a wedge shaped end through the wood. The oblong slots are made across the grain of the wood, presumably so as not to split it. These ribs are from old (probably early 20th century) British moulds. I have not tried this.
The slanted teeth allow the pawl to climb out and away from one tooth and ‘click’ back against the next tooth as the rib is pushed along. After each incremental re-positioning with the left hand the right hand advances the feed lever of the drill press to make one hole. Each cycle takes about one second. The drill press is set to spin the drill at a high speed so the chuck and drill can be jammed down quickly after each advance of the rib.
One of each ( #1 through #4) ribs showing the variation in hole spacing. The ribs are placed in the mould in order; 1,2,3,4,1,2,3,4,…
Sewing Holes for Wove Moulds
The sewing holes for my wove moulds follow a simple 1,2,3 diagonal pattern and are spaced to put a stitch between each third pair of laid backing wires. This can be seen in the photo where a wove backing is in the process of being stitched to the ribs. The backing wires will provide a support for the fine wire cloth that will be sewn down in another step. I use the same spacing of laid backing wires for all wove moulds, so one serrated rack is sufficient for all.
This drill press has a table that can be tilted and is prone to getting out of alignment. A dial indicator mounted in the chuck can be rotated by hand to check this. Small taps from a dead blow hammer are usually enough to correct misalignment. If the spindle is not true to the table (90 degrees in all directions) the holes drilled for rib pegs will tend to push the ribs out at odd angles. This introduces tensions into the structure that may throw the mould out-of-flat and/or out-of-square.
Setting the Drill Press Fence
The center of the rib peg hole, having been calculated, is scribed onto a test block, usually an off-cut or extra piece from the batch of moulds being made.
The hole to be drilled here (in this test piece) has been calculated to make the narrow top edge of the rib end up high by about .010″. This bit of extra wood will allow the ribs to be leveled after the mould has been assembled. Different types of mould will require the ribs to be set at different levels. This is to account for the differing arrangements of laid, bridge and chain wires that will rest on and be sewn down to the ribs. Drawings at the bottom of this post may make this more clear.
A fence is adjusted by eye to drill to the center of the mark. It is clamped to the table with two C-clamps and a test hole is drilled with a brad point drill.
A rib is inserted…
…and the depth of the recess is checked. The drill press fence is then re-adjusted as required before drilling the holes in the actual frame pieces.
Drill the Rib Holes
Try to put the point of the drill exactly in the middle of each mark. I sit on a chair so my eyes are nearly at the level of the table and use magnification to see better.
The top edge of the mould frame piece rests against the fence. The hole is drilled from the inside of the mould where the marks have been made. The depth stop of the drill press is set so that only the sharp point of the drill pokes through the other side.
The frame piece has been flipped over to show the tiny hole created by the point of the drill. Using the fence, the piece can be positioned so that the drill point will ‘seek’ the hole to finish drilling from the other side. This way the hole can be finished neatly without tear out.
As mentioned in a previous post some moulds have ‘blind’ holes that don’t pass completely through the frame. In my way of thinking a through hole is better. I have repaired old moulds where the shorter ‘blind’ rib ends weren’t adequately pinned to the frame, allowing the frame sides to spread apart. I also think that a mould with full length rib pegs might dry out a little more quickly after use, possibly helping to prevent decay. There are no concealed pockets to trap moisture (after any amount of use all parts of a mould will be thoroughly soaked) and the exposed end grain of the ribs may actually help wick away the moisture that has accumulated. Moisture enters and exits wood more readily through end grain than it does across the grain.
The sides of the frame are lightly sanded to catch and remove any ragged fibers around the edges of the holes.
Finished rib holes.
A rib seated in its hole in the frame.
The same rib from the other side.
When inserted the ribs should be held square to the frame. Individual ribs will usually curve slightly one way or the other. Turning a rib 180 degrees and checking it twice from the same side will reveal this. If the variation from square is the same both ways the hole is drilled perpendicular to the frame. If not the hole may be slanted.
A waterbar is a small extra rib that lies closely along the short ends of a mould. The wires of the mould aren’t sewn to it, it just touches the bottoms of the wires that cross it. Notches are routed into the frame to hold the ends of a waterbar. In Britain what I call “ribs” are called “bars”. So “waterbar” might translate to “water rib”. This could be a shortening of the awkward-to-say “de-watering bar”. These little ribs are intended to improve drainage along the short ends of a mould just under the edge of the deckle. Ribs provide pathways for water to flow down and away from the paper being formed on top of the porous wire facing. Including theses small de-watering ribs makes sense for single-faced moulds. These moulds suffer from poor drainage in the areas between ribs so the fibers are deposited on the wires there in a thinner layer. Thicker areas, known as ‘shadow zones’ form along the ribs where drainage is improved by the presence of those ribs. It follows that an extra rib positioned right under the edge of the deckle might improve drainage and help to form a substantial deckle edge there, too. But I’m inclined to think that waterbars are not needed for double-faced laid or wove moulds. In these moulds a layer of backing wires provides more pathways for water to flow along. This more complicated wire structure improves drainage and makes formation very even over the entire top layer of wires and eliminates the shadow zones. I would argue that no extra help from waterbars is needed for these moulds that include an extra layer of wires. Many people make their own wove moulds which must have backing wire of some sort to function well. Most, if not all of these moulds do not have waterbars and don’t seem to need them.
(Though I have long suspected that most waterbars are ‘vestigial’ and unnecessary I do not follow my own advice. Waterbars are still found on all of my moulds.)
This drawing shows the waterbar and how it relates to the inner margin of the deckle.
Mould sides drilled and ready for assembly.
Because the drill leaves a little bump where its point exits the other side of the mould frame I drill only every 5th hole in a pass. This way the bump will hang over the edge of my drill press table and can’t affect the alignment of the next hole as it is drilled. Here I’m on the third ’round’ having just drilled the 3rd and 8th holes. (The gap visible between the work and the fence is not normal. My hands are holding the camera and the piece has shifted on the table.)
I don’t like the idea of the bump preventing the frame piece from resting completely flat on the drill press table (having already gone to the trouble of aligning it with the dial indicator). When a side is 1/5 finished I pare off the bumps on the back. Then the piece is returned to the drill press to repeat the process with the next several holes, again every fifth hole (depending on the size of the drill press table). This process isn’t difficult and doesn’t take significantly longer. This is just one more detail that’s intended to improve the outcome.
Making Fine Adjustments
When setting up the drill press the first hole drilled into a test block inevitably needs to be moved a little closer or farther from the top edge of the frame. Here is a simple way to accurately re-position the fence. In the photo I’ve clamped a scrap block of wood with a true flat end tight against the fence. After loosening the two clamps that secure the fence an appropriate shim can be inserted. Then the fence is pushed up tight against the shimmed block and the C-clamps re-tightened, re-positioning the fence BACK by exactly the thickness of the shim. Block and shim are then removed. If the shim is placed FIRST (before clamping the block in place) the fence can be moved FORWARD after the shim is removed.
After waterbar notches have been made in one end of all of the mould frame pieces the stop (shown here clamped to the tablesaw fence) has to be moved to the other side of the router bit.
This is because the notches must be cut from the opposite direction on the other end(s).
Placement of Ribs for Three Types of Mould
A single faced laid mould will have the ribs set very close to the top of the mould frame. After the tops of the ribs are leveled they should be lower by a little more than the diameter of the laid wires. The level described by the top edges of the ribs is indicated here and in the two drawings below by the lower line and arrow. The upper line shows the top edge of the frame.
For a double faced laid mould the tops of the ribs should be set considerably lower as shown above.
The edges of the wire cloth wove surface generally rest on top of the mould frame. The ribs of a wove mould need to be set at a level to accommodate the diameters of the backing and bridge wires that support the wove facing.
Paper Mould ribs connect with the outer frame by means of small pegs formed on their ends. These rest in holes bored into the frame at regular intervals. The ribs on the left have finished pegs; on the right they are only partly completed. The tool in the middle is used to help machine the twelve sided pegs.
The end of a mould frame is used as a gauge to set the saw fence so the ribs are cut to the exact same length. I drill the rib holes completely through the sides of the mould so the ribs are the same length as the width of the mould. Many moulds are made with ‘blind holes’ drilled only part way into the frame.
A rib is cut to final length. The other end has already been trimmed so both ends are left smooth and square.
1/8″ diameter holes are drilled where the rib peg will meet the shoulder of the rib. This is a stress point and the hole, at least in theory, spreads the stress over a wider area to help avoid splits here.
A cut is made to establish the shoulder of the rib where the peg starts. This is a finish cut and will not be altered when the peg is shaped.
The shoulder is cut back a little so it won’t quite touch the inner side of the frame. You can see that there will be a small space between the body of the rib and the inside of the mould frame. The end of the peg will be exactly flush with the outside.
This is a rough cut made to remove most of the waste before the peg is shaped.
The stub will be shaped into a peg like the finished one on the right.
Ribs for three identical 12″ x 18″ moulds, ready for final shaping.
Shaping the Pegs
Holes are drilled in a few ‘offcuts’. These will be used to test and adjust the fit of the rib pegs. Later the same drill will be used to prepare the mould frame to receive the ribs.
This spiral router bit makes a shearing cut while pushing the fibers upward for a clean cut. The bit is called a down-cut spiral bit but this router is mounted upside-down so in this case a down-cut becomes an up-cut.
The steel table saw fence is adjusted so the peg can be machined for its full length without damaging the previously cut shoulder. The wooden fence guides the rib peg tool while it is slid back and forth and keeps the rib centered over the router bit. The height of the router bit establishes the diameter of the faceted peg.
After making a test cut the dial indicator can be used to make slight adjustments to the height of the router bit to give the peg a good fit with the holes in the test blocks.
The tool creates a 12 sided rib peg. Later on the facets will be slightly compressed as each peg is twisted into a sized hole in a plastic gauge. This will leave the pegs almost perfectly round and ready to fit into holes in the mould frame.
Details of the Rib Peg Tool
These are peg tools of an older design that I used for many years. Wood shrinks different amounts along and across annual growth rings. For this reason the rib pegs turned out oval instead of round during part of the year. Thus the blue tape added to the two oak tools to correct this problem. The darker tool made of mahogany (which is more stable and shows a smaller difference between radial and tangential shrinkage) was less troublesome. The small wooden ‘scewdriver’ is used to tighten the two recessed thumbscrews which clamp the rib while it is being shaped.
The new tools have ends shaped from plywood which doesn’t change dimension with seasonal humidity.
These are the ‘cores’ for four different rib peg tools. Each is made for a different size rib. From left to right 15/16″, 3/4″, 5/8″ and 1/2″.
The parts of the tool are held together by the plywood ends.
Another improvement is that the tops of the ribs rest on a ground steel plate.
The heads of the hex bolts are tightened with finger and thumb. This works well and no separate tool is needed unlike in the older design. The pressure bar has been slid to the right to show the inserted plastic pad. The bar is correctly aligned in the previous photo.
The two flat head machine screws have smooth rounded ends that can be adjusted to keep the rib centered over the steel plate. You can see the shiny ends in the two photos above.
The grooved pressure bar centers the thick (bottom) side of the rib while the peg is being shaped.
This slide show illustrates the steps of routing a peg on the end of a rib. Notice how the tool makes a complete rotation in 12 steps; each corresponding to one facet of the peg. Keep in mind that for each step the tool is slid back and forth so the router can shape the complete length of the peg (this doesn’t show well here). The router bit only machines the facets of the peg and doesn’t quite touch the shoulder of the rib.
This step is not too exciting but is important. The two long sides of a mould need to be drilled to receive the rib pegs. Marks are made to show the locations of the holes to be drilled. If the hole spacing is erratic or not symmetrical the mould can be thrown out of square. And for a laid mould the notches made in the rim of the deckle should match up with all the chain wires whichever way the deckle is set on the mould. For a pair of moulds sharing one deckle it becomes even more important to lay out the spacing accurately since the deckle should fit either mould equally well, both ways.
First the exact center is found and marked on the inside face of one of the two side pieces.
The sides are clamped together so the ends line up exactly and the upper sides touch each other. Then the rib spacing is carefully laid out using a square and a sharp hard pencil. This is done from the middle to one end, marking across both pieces. I am right-handed and tend to hold the square with my left hand and the pencil in my right, working from left to right as shown here. I have accentuated the marks with ink so they’ll show up better in the photos. Notice that the (marked) center of this mould will lie halfway between two ribs. Thus the measurement between the center mark and the first rib line is half of the rib spacing. This mould has 1-1/8″ rib spacing so the first mark is 9/16″ from the center.
One piece is turned end for end and inverted so its top edge rests against the side of the other piece. Once again the ends are clamped between blocks. The blocks are offcuts from the mould frame pieces.
A scrap block with a true 90 degree end is used to carry the pencil marks from the lower piece over to the one that is set on its edge. Using a hard, sharp pencil (I use a 6H) it is possible to locate the point of the pencil partly by feel (where it has indented the wood) so that the square block can be snugged up against it, helping with accuracy.
In this photo I have set one frame piece behind rather than on top of the other. Sorry for any added confusion here; either way works the same. Marks should extend all the way to what will be the inner top edges but need only extend far enough down to cross the place where the rib peg holes will be drilled.
The marks have been transferred and now one piece is fully marked.
Both pieces are turned end for end and laid flat to finish marking the other side piece.
The reason for going through this process is to make the marks along opposite halves of the mould mirror each other (from the center out). This is important because a deckle can be laid on a mould in two possible ways. If the rib spacing is truly symmetrical the little notches under the rim of the deckle will fit neatly over the chain wires either way. If the chain wires are erratic some of the notches will need to be widened or doubled. This might be OK but does not look good!
If a pair of identical moulds are being made for use with one deckle the four sides of both moulds will be exactly the same length. The marks can be carried over to the second pair using the method shown in the photos above.
The last step of the marking process is to carry the marks over and onto the top edges using a marking knife. These marks will be used to help align the ribs and later the chain wires of the laid facing.
To check your work slide one piece over to offset the marks by one space. This will reveal errors in the spacing. I once made the mistake of making a mould with one narrow rib space. This test would have caught the error in time.
To make the mould and deckle fit together properly you need to know the deckle overlap (A), the width of the deckle (A+B) and the amount of space to leave between mould and deckle (C). More detail on this will follow later in this post.
The mould frame is joined at its corners with dovetail joints. The two protruding parts on the left are called ‘tails’ and the three parts on the right are called ‘pins’. Remembering this will make it much easier to understand this post.
Using the hollow ground planer blade the mould frame pieces are cut to exact length with ends that are square.
Using one piece of a mould frame to scribe a line on another. All pieces are scribed this way to begin marking the dovetail joints. Those with ‘tails’ (the short sides of the mould) are scribed on all four sides and those with ‘pins’ (the long sides of a mould) are scribed on two sides.
The scribed line defines the bottoms of the joints.
I use a small block of wood with four sharp steel pins to mark the dovetail spacing. The marks are made on the outsides of the long pieces to mark the pins…
…and on the ends of the short pieces to mark the ends of the tails.
This gauge is used with a marking knife to scribe angled lines for the dovetails. Above, the long side of a mould is being marked on its end for pins; below the short side of a mould is being marked on its side for tails. The longer side of the gauge is always pressed against what will become the top of the mould frame.
The tails are marked the same on both sides; the pins only on the outside. The tool is carefully set to make a slanted mark that matches up exactly with the previously scribed straight mark (where they meet at the corner). After the tool is set it is used to mark all of the joints being made; pins and tails. After all parts are scribed the brass blade is re-adjusted to mark the second dovetail and the process repeated. Then the blade is flipped to reverse the angle and the process is repeated to scribe the other two sides of the dovetails.
The short pieces which will form the ends of the mould showing the ‘tails’ marked with parallel marks on their ends and angled marks on their sides.
The long pieces which will form the sides of the mould are marked with parallel marks on their sides (difficult to see) and angled marks on their ends.
Rough out waste wood
I usually make a few moulds at a time. If the joints are identical it is easier to do some of the work by machine. When making one mould at a time it might be easier to do more of the work by hand.
This tool is used to hold the parts straight up at 90 degrees to the table so accurate cuts can be made at the ends using the hollow ground blade. Here a block of wood is screwed to the side of the tool to hold the pieces at an angle that matches the dovetails on the pins (6 degrees here).
You have to keep your wits about you to keep from making mistakes. The pieces must all be oriented the same way with the (smooth) tops on the same side and the outsides facing forward. The fence of the tablesaw is re-set for the cut between each pair of pins. The block that establishes the angle is moved to the other end of the tool to reverse the angle for the other sides of the pins.
Notice that the scribed lines are still clearly visible. They will be used to guide the chisel when the joints are pared by hand to their final fit.
Removing the block holds these pieces at 90 degrees to the fence. Now the saw is tilted to 6 degrees to cut the angled sides of the tails.
The short pieces on the left are extras. I always make a few shorts that are used as test pieces when making adjustments.
Again, the scribed lines are left to guide hand work.
Machine trim tails and pins
Now the shoulders of the tails are trimmed using the hollow ground blade (now set at 90 degrees). This is not a rough cut; it will be the final cut for this part of the joint. The dial indicator makes it possible to make very fine adjustments. Once the fence is set all of the parts are trimmed exactly the same.
The machine work is finished for the tails.
The space between two pins is being routed out to establish surfaces at the bottom of the joint. The router bit is set to exactly match the thickness of the frame parts. The block of wood at the far left is a stop that is clamped to the tablesaw fence to limit the cut.
The pieces are only routed out a little bit…
…from both sides. The little ledges make it easy to position the chisel to trim out the bottoms between the pins.
Final fit by hand
Now the joints will be pared by hand using the scribed marks to guide the chisels.
The flats between the pins have been chiseled out using the routed surfaces as guides. These surfaces should ideally be flat but it is more practical to make them ever so slightly hollow. When the back of a chisel is laid flat there it should not rock on any high spots. (Better to have low spots). Using the scribed parallel lines to start the chisel, the sides of the pins are refined, using the slanted lines as guides. The photo above shows two sides just started. The pins are pared from one side only; there are no lines scribed marking the back side of the joint.
The tails are pared in a similar way after the flat between the tails is chopped out at the scribed line. The chisel is started in the angled marks and the parallel marks are used as visual guides. The chisel can be located in the scribed marks partly by feel, though I have to use my head mounted magnifier for most of this hand work. The tails are pared halfway from each side; the angled marks have been scribed on both sides.
The finished joint. It is usually necessary to pare little bits off here and there to get the joints to fit just right. Some folks would want to cut the joints entirely by machine which is certainly possible. But a slight miscalculation using a machine makes it easy to make a lot of scrap in a hurry. I prefer a safer approach and find it satisfying to do this part by hand.
Mould frames after final fitting. There are a few extra pieces here that won’t be used. The four pieces of lighter colored wood are an experiment. They will make an A4 size wove mould made entirely of Larch.
More detail and a few tips.
For most of my career A (the deckle overlap) measured 3/4″ and B measured 1/2″. The total width of the deckle was 1-1/4″. For the space between the mould frame and the inside of the deckle (C) I use .015″. If a mould was to make a sheet 12″ x 18″ the drawing would work like this: For the short side 12″ (N) would be added to twice the deckle overlap (A) to give 13-1/2″. From this twice the desired space (C) is subtracted. The result for the two shorter frame pieces would be 13-1/2″ minus .030″. Calculating the length of the deckle pieces is easier; they would measure 12″ plus twice the deckle width (2-1/2″) or 14-1/2″. The same calculations are made for the longer pieces, substituting 18″ for 12″ at (N).
This measuring tool is better than using a tape measure. The beam is scribed in 1/2″ increments and should be long enough for your largest mould. The small block with white plastic guides is clamped so that its near end aligns with the desired mark. The trimmed end of a mould part can be pushed against the block on the left and scribed at its other end for an accurate measurement.
Here the tool is set to mark the long side of a 12″ x 18″ mould so the moveable block has been set for exactly 19-1/2″ (using the above calculations). The .030″ shim reduces the length to create the .015″ space at both ends.
This is a rough piece of wood, used as an example. But if it were an actual frame piece the left end would contact the shim. This would reduce the length by the desired .030″ when the length is scribed as shown here.
If the mould is to be sheathed with brass sheet two additional shims are added. They are the same thickness as the brass that I use (.017″)
The saw is being set to cut at the scribed mark made using the measuring beam. If the deckle pieces and mould frame pieces are all measured with the same device the results are more predictable and the fit is likely to be better.
Since I use epoxy to glue the joints they will be rigid. If slightly out of square pieces are clamped and glued they will likely force the frame out of flat. To avoid this problem any out of square pieces can be corrected with couple of swipes using a block plane and the method below.
The blade is very sharp and set for a fine cut. The middle is planed hollow as shown above. Then the bed of the plane behind the cutter is set firmly down on the low side and a fine cut taken off the high side. Check for square and repeat if needed. This adjustment only needs to be made for the longer dimension as shown above. The short dimension isn’t as important.
Different dovetail spacings each need a scribing block.
When trimming the shoulders of the short sides you can check the fit like this.
Raising the saw just enough to score barely across the scribed lines leaves a visible line that helps when paring the sides of the tails.
Before routing between the pins the router bit is set at exactly the thickness of the mould frame pieces using the dial indicator.
Note: (This batch of small moulds is made with different dimensions than my old standard; the frame pieces are 7/16″ thick (.437″ on the dial indicator shown above). For years the small moulds I have made seemed over-built. I now make smaller moulds a little ‘lighter’. These moulds have 11/16″ deckle overlap, 1-1/8″ x 3/4″ deckle parts. The frame parts measure 7/16″ x 1-1/8″. The ribs are 5/8″ deep with 3/16″ diameter pegs. The space between mould and deckle stays the same at .015″ all around.)
These routed ledges make it easy to trim the bottoms of the joints flat between the pins.
The frame piece dogged flat on the bench for trimming between the pins.
The joints of the pins are not scribed on the inside. Chiseling off these corners keeps the chisel from splitting them off when the joint is pared from the other side.
It helps to cut these grooves (with a small chisel held at an angle) before paring the sides of the pins. Then the chisel is kept just above these grooves so the parings can easily fall away. If the grooves aren’t there the uncut fibers of the wood at the bottom will pinch the chisel there making it harder to control. The corners can be cleaned out after sides are made flat.
A sharp chisel’s edge can be started right in the scribed line…
…and pushed straight down to trim between the tails. The piece is flipped and the process repeated from the other side.
With a little careful guidance (and visual magnification) a sharp chisel will seem to find its own way into the scribed lines to start the paring cuts.
A finished pair of tails.
Pins and tails fit together to make a very strong joint.
The wood that has been seasoned for making ribs now needs to be straightened and shaped to a distinctive ‘tear drop’ shape. This is narrow at the top so as not to obstruct the flow of water while forming sheets yet wide enough at the bottom to form pegs at the ends. These rest in holes to connect the ribs to the frame. Later posts will discuss shaping pegs, drilling for the stays and sewing, and otherwise finishing the ribs.
This drawing was made to calculate and keep track of the angles and dimensions of two sizes of ribs. The ribs that are being made in the following photos are the smaller size; 5/8″ deep with 3/16″ diameter ‘pegs’ centered 1/2″ from the top. Single faced laid moulds have ribs that are 1/16″ wide at the top. Double faced laid and wove moulds use ribs with 3/32″ wide top edges. The width at the bottom is not critical but the ribs need to be thick enough there to form the pegs that fit into holes in the mould frame. In addition to the sizes above I have used ribs that are 15/16″ deep for large moulds and even 1-1/8″ deep for very large moulds. And I have used 1/2″ deep ribs for very small ‘test’ moulds.
The rough stock which has been previously seasoned. (See previous post)
One side of each rib is flattened on the jointer.
Then the top edge is also made flat and straight, at 90 degrees to the side.
The ribs are sawn slightly oversized at the proper angle. The angle depends on the size and type of mould. For these moulds the angle is 7 degrees off of perpendicular. (Since the wide sides will form an angle of 14 degrees subtract half of that from 90 degrees) This makes a slightly acute angle of 83 degrees.
Then the rough side of each rib is sawn to the right angle on this suction fixture. Here the saw is set to create an angle of 14 degrees but leaving the rib a bit thick for one more trim.
This shows how the ribs are held to the special attachment with suction supplied by a shop vac. as they are fed past the rip saw blade.
The rib on the right has been jointed, straightened and had its bottom sawn to 83 degrees. The arrow points to the juncture of the two jointed sides; this angle is now 90 degrees. This corresponds to step 2 in the photo below.
Stage 1 is the rough stock. Stage 2 has the left and top faces jointed and the other two faces sawn to the correct angles. (So far in this post stages 1 and 2 have been completed.) In stage 3 the stock will be straightened once again and reduced a little more, but with the 90 degree angle on top corrected to 97 degrees. ( When the ribs are installed in the mould ‘standing up straight’ the top surfaces will be aligned with the top of the mould). Step 4 shows the finished stock. The reason for reducing the dimensions of the ribs in two steps is to make them straighter. They will distort slightly each time material is removed; this way they are likely to distort less the second (last) time.
The wide face of each rib is once again flattened and the top edge jointed, but not at 90 degrees this time. This shows the jointer fence being set to 97 degrees to joint the tops of the ribs.
The ribs are now trimmed to their final depth. It is best for the fence to have an angled edge to match the top angle of the rib. This is easily done by setting the angle for the rib bottom on the saw and feeding a thin strip of wood through. Then it is clamped in place as a temporary fence to saw the wood accurately to width.
The ribs are ready for the second and last run through the vacuum fence. At the upper right you can see the 5 suction holes that hold the rib against the fence. The clear plastic piece at the top can be adjusted to help hold the ribs in place. The vacuum hose plugs into the large hole on top.
The ribs are pushed through one after another, each pushing the previous one, and they fall off onto the floor.
The rough side of each rib is now planed smooth. A block of wood spans the cutter head and presses the rib down against the in-feed and out-feed tables. First the rib is pushed and then pulled to keep the right hand at a safe distance. The same method of adjusting the tablesaw fence is used here as was previously used in thicknessing the mould frame. First a test piece is sawn on the vacuum fixture and planed smooth. Then it is measured to see how much more needs to be removed to end up at the right thickness. The fence is adjusted by that amount using the dial indicator.
The bottom edges are rounded using a rounding router bit and an angled fence. A narrow band of the rough (but accurate) surface is left. After the ribs are complete and ready to install in the mould frame this will mostly sand off with a few swipes of a sanding sponge.
If the rib stock was correctly made the pieces will slide easily into this jig which will be used later to shape dowel-shaped pegs on the ends.
Thus 5/32″ radius round over bit was used to shape the bottoms of these ribs.
Angled edges on the fence allow the rib to be rounded in one pass each side.
Another view of the vacuum/suction fixture. The saw blade can be tilted in the saw to prepare ribs of different angles.
The rib is sucked tightly against the angled fence while being pushed through.
The wood for making Paper Mould frames has been prepared to make pieces that are relatively stress free and stable. Now the stock will be shaped to its final dimensions prior to cutting to length and joining at the corners with dovetails.
Shown above is a block of poplar that I shaped to demonstrate the method I use to make the frame pieces of even thickness. I used exaggerated angles to make it easier to see.
To begin one side of each frame piece is jointed perfectly flat on the freshly sharpened jointer. I am experimenting with better guards for machines to make them safer to use.
Next one edge is also jointed perfectly straight and at exactly 90 degrees to its previously jointed side.
The wood rests on its newly flattened side with the jointed edge against the tablesaw fence. It is sawn (with the rip saw of the previous post) at precisely 90 degrees to the jointed face. The fence is set so the pieces end up about .015″ (1/64″) wider than the intended final width. They will all end up exactly the same width and the slightly rough edge will be left that way until after the joints are cut. This makes it easy to identify the bottom edge of the mould frame. It also helps avoid mistakes as the pieces are put through all of the steps to create the dovetail joints. Even though the sawn edge is rough it leaves a precise, square, straight edge to measure against. The wooden ‘featherboard’ pressing on the piece being sawn means my fingers don’t get close; a push stick is used to finish the cut.
This photo shows how the home-made dial indicator fixture can be used to help adjust the fence very precisely. As the fence is moved laterally, the dial on the left will measure the change.
The first step to thickness the wood uses the rip saw raised to just over half of the width of the frame pieces. It is set at a slight angle; about 1/3 of a degree. Each piece is sawn in two steps to create a very shallow ‘V’ shaped depression. This piece was withdrawn partway through to show the process.
You can see the shallow V-shaped space when a straight edge is placed there.
If the saw is sharp and the fence is straight this will leave edges that will measure exactly the same width all along the length. When placed rough side down on the jointer only the outer edges will touch the table. When pushed through the jointer the pieces will be planed to a precise thickness. It works very well! Here a test piece is used; first sawn and then jointed at the end. This is measured with the vernier calipers to see how much the table saw fence needs to be adjusted, with the help of the dial indicator, to achieve the desired thickness.
The mould frame stock is finished and ready to cut length. Each piece has one rough side and three smoothly jointed sides and all are virtually identical in thickness and width. And, as you can see, the pieces are very straight.
To test to see how well a jointer is working see how a freshly jointed piece acts by gently moving one end as shown in these two photos.
If the piece pivots on the middle as above the piece has a ‘belly’. The star indicates the approximate pivot point.
These two photos show a better outcome…
One end will move and the other stays in the same place. It pivots near the star at the right. This shows that the piece is ‘hollow’ (microscopically) but this is better than having a belly. Woodworking planes work this way. If you are preparing to join two pieces of wood, set the plane for a fine cut and try to make the edges hollow. The tool will not allow that to happen (except to an insignificant degree). The next 4 photos will attempt to show a machine process of slightly hollowing a piece first, then jointing it flat. It ends up sounding kind of insane but what I’m trying to describe becomes pretty intuitive once you get the hang of it.
The guard is opened so the piece to be worked can be dropped in. The jointer is set to a very fine cut; about .005″-.010″. This is possible because the wood is already very flat.
The workpiece in place with about an inch hanging over the out-feed table.
The guard is pushed in and with light pressure at both ends the piece is started here, moved fairly rapidly from right….
…to left and ending in this position. The ends aren’t trimmed at all. This is repeated 2 or three times and has the effect of slightly hollowing out the middle, while removing any ‘hump’ or ‘belly’. Don’t move the guard, just pull the piece back through to start again. You can hear and feel when the knives can no longer reach the wood to cut any more. Then the piece is pulled completely out to the right, lifting slightly to clear the knives. This sounds harder than it is. Being slightly hollow the ‘board’ now rests on its ends so it can move into the cutters without any tendency to rock. As the left end of the piece slowly passes the knives a true plane is established on the bottom edge of the wood which continues to move along to rest on and be supported by the out-feed table. As the board is slowly fed past the knives, that plane is extended until the right hand end leaves the in-feed table and passes the knives, finishing the cut. This is repeated one more time to remove a slight ‘divot’ that will likely occur at the left end; this last pass especially being nice and slow.
The thicknessing method.
Here is the poplar ‘demonstration block’ being sawn at a slight slant. I set the saw at 3 degrees (instead of the usual 1/3 degree) to make it easier to see. The usual angle is somewhat arbitrary, just enough to create two clean edges for the wood to ride on without having to joint too heavily to remove the saw cuts.
The hollow is visible beneath the straight edge. When the piece is turned over only the outer edges will ‘ride’ on the jointer table as the saw cuts are planed off.
Measuring the thickness at numerous places along both edges with this vernier caliper showed variation of less than .001″. (1/40mm) The measurements hardly strayed off the line possibly showing variation closer to +/- .0005″!
After jointing a smooth face replaces the rough sawn one.
Measuring wood in thousandths of an inch might seem ridiculous. But being able to control dimension with basic low-tech tools is kind of satisfying. And it makes the later steps easier. Wood will always move; these ‘perfect’ pieces of wood will not stay that way but they will likely be closer. I am convinced that the care taken now pays off in the long run as the pieces of a mould end up being more ‘relaxed’, each doing its part and not working at cross purposes. At least not as much.
The question comes to mind: “Why not just use a thickness planer?” Early on I did. Even for ribs, though that was soon abandoned. The rollers mashed one side of the wood and distorted it. Probably the need to find a way to make the delicate ribs without damaging them led me to this way of making the frame stock. I can’t remember the entire process of discovery.
In my shop a thickness planer is a valuable tool but I have not sharpened mine in years! It is a lot of trouble to change the knives. I use it to save time when shaping larger pieces of wood. If wood is jointed or planed with dull knives the edges are actually ‘pounding’ on the wood as well as cutting. This smashes and bruises the surface. When the wood gets wet smashed areas will swell and ‘rise up’ making the surface rough. Wood cut with very sharp tools won’t do this as much. I hardly do anything to smooth the wood of a paper mould after the wood work is done. Edges are slightly rounded with a plane and the outsides are smoothed just a little with a fine sanding sponge.
More on the thicknessing method.
In the drawing above the rectangle on the right represents the desired final width dimension (B) of the mould frame in cross-section. On the left the rough, DOTTED area represents the part to be sawn off. This in preparation for planing off (on the jointer) the DASHED area. If you try to saw the frame stock to width in one pass some problems may occur. To make the bottom dimension (A) the same as the top dimension (A2) will take very careful adjusting of the tablesaw. No matter how careful you are the two are not likely to end up the same. For one thing at the top edge of the wood (along C2) the circular saw blade will be cutting 1-1/4″ to 1-1/2″ above the tablesaw surface while along the bottom (at C) the wood will rest on that surface. Dimension “A” is likely to remain very consistent while dimension “B” may vary a bit with slight differences in pressure as the wood is fed through the saw. Circular saws can ‘flutter’ which is likely to cause a slightly more irregular cut at the top than at the bottom. This may leave a surface that is not functionally flat; it may rock slightly on the jointer. If it rocks at all, the thickness will not be consistent after the rough saw marks are planed off.
Trimming the frame piece from both sides with the saw set at a very slight angle reduces or eliminates these problems and it’s so easy! First there is no need to carefully adjust the tilt of the saw to try to make the top and bottom edges equal in one pass. The tilt of the saw is not at all critical; just enough to create the shallow depression along the center but not so deep that an excessive amount of wood needs to be planed off. (About 1/3 degree for moulds) The saw cut only needs to be half as deep so there is less opportunity for a ‘wobbly’ or ‘fluttery’ cut. Dimension “A” at BOTH top and bottom is ‘defined’ by the distance between the fence and the saw blade at the level of the table. This is as accurate as you are likely to get on a tablesaw. Since the jointer knives are set to very close tolerances the two sides will end up virtually parallel. When being pushed over the jointer the piece rides on the edges only (C) so it can’t rock.
For yet one more attempt to explain this in words check out my reply to the comment posted below.
The wood for moulds, ribs and deckles has been seasoned, straightened and trimmed to near final dimensions. At this point I pause to get the necessary tools tuned up and ready to go. (I’ll post general information first, and include more detail at the end for those who are interested). These are current sharpening methods for the tools I depend on the most.
This 8″ Hollow Ground Planer saw blade plays a major role in my method for making paper moulds. Many sharpenings have reduced the diameter of the saw which started out exactly the same as the new one behind it.
I found a few of these on Ebay. I don’t know if they are still made.
When the saw is new the teeth are all filed nearly straight across like this and it doesn’t cut well.
The teeth should be filed at 15 degrees like this. Every fifth tooth is a raker which is filed straight across and at a lower level to cut slightly below the tips of the cross cut teeth. This blade cuts very smoothly and I use it a lot for the finer work making moulds. Steel isn’t as hard as carbide but is less brittle so the the teeth can be shaped to sharper points. It seems to cut more freely and with less chip-out on the relatively soft woods used for moulds.
This is a rip saw. Its teeth are all shaped like little chisels and it is used for cutting wood parallel to the fibers (‘ripping’). I’ve learned how to use it in combination with a sharp, well-tuned jointer to create perfectly straight pieces of perfectly even and consistent thickness. This and the hollow ground planer are the only two saw blades needed for making moulds.
This is my home-made saw filing vise which is used to keep both types of saw sharp.
This is a home-made stake and anvil that I use occasionally to put ‘set’ in the teeth of the rip saw. Used with a hammer and punch this tool is used to bend the tips of the teeth to create ‘set’. The cut made by a saw must be wider than the saw’s body to prevent binding. The ‘anvil’ is just a hardened bolt with its outer edges eased to provide an angled striking surface.
A very sharp, well tuned jointer is essential for this method of making moulds. On top is a very simple tool that holds a dial indicator to check for proper alignment of the in-feed and out-feed tables of the jointer.
There are countless ways to sharpen. I have recently discovered a very effective way to hone jointer knives. I purchased an old surface grinder some years ago to help me make bookbinding tools. It came with a magnetic chuck, shown here dismounted from the machine. The top surface is perfectly flat and can be turned into a powerful magnet with the turn of a lever. This can hold the jointer knife as well as this roller assembly firmly in place to create a controlled honing angle. A more detailed description is given in the second part of this post.
Another simple shop-made device holds a dial indicator for setting the jointer knives. This tool also gets used a lot for making small adjustments when using the tablesaw, jointer and router table.
This machine works very well for sharpening chisels. I’ll use the four chisels shown for paring the dovetail joints of the mould frames and for detail work on the deckle joints.
A Deeper Dive…
The information given above just scratches the surface. Below is more detail for those who are interested. There is still much more to know and to discover.
Marks on the saw vise show the correct angle to hold the file. The saw must first be ‘jointed’ on the tablesaw. The saw is set for exactly 90 degrees and lowered so the teeth are just below the table surface. A carborundum sharpening stone is held directly over the saw blade. With the machine running the saw is raised EXTREMELY slowly until a few sparks are visible. (Dim the lights). This will dull the teeth slightly so that all are at the same height. The teeth should be altered the smallest possible amount. Only enough to show a tiny shiny spot on each tooth (minus the rakers).
Teeth are filed alternately on both faces until the shiny spots just disappear, leaving the teeth sharp and all at the same height. The raker teeth must be jointed in a different way with each tooth held at ‘top dead center’ in the vise. Careful adjustment and a file used with a block of wood joint the cutting edges about 1/64″ lower than the other teeth. Then they too are filed sharp until the jointed spots disappear. The angled teeth slice the wood fibers like little knives while the straight teeth rake out the waste between like little chisels. Since the higher, angled teeth contact the wood first the the fibers are sliced, not ‘torn’, leaving a clean surface.
The saw gets reversed in the vise to file alternating teeth.
I rub the file on a file card frequently. I spray a little WD40 on the card which helps the file cut smoother without ‘chattering’.
This rip saw is much easier to sharpen. Here, it has been jointed on the tablesaw. You can see the shiny spot that now needs to be filed away.
First the front faces of the teeth are dressed smooth. Here the saw is positioned with a tooth at top dead center. This way you can angle the file to ‘feel’ the correct relief angle while filing. The narrow margin visible along the edge of this tooth is where it was jointed. This saw has very little ‘set’ remaining and that will soon need to be addressed. Less often a saw also needs to be ‘gummed’ which means the gullets between the teeth are filed deeper and the teeth re-shaped as needed.
The tops of the teeth are filed until the shiny part just disappears.
The saw vise can be adjusted for different diameter saws.
The stake and anvil are adjusted with shims so the blade sits flat on the ‘anvil’ (a large hardened bolt head that has been ground to a slight bevel at its edges). A tooth is positioned to hang over the edge just enough to be bent slightly with a punch driven by a hammer blow.
The center bolt can be moved for different diameter saw blades.
This tool is just a sturdy piece of wood as long as the longest table with three screws on the bottom. A hole at the far end holds a dial indicator which is adjusted to agree with the other three points to define a plane. You can then move the beam around to measure misalignment of the jointer tables. They should be exactly parallel to each other (even when set at different levels). Once you get the machine aligned this step doesn’t need to be repeated. I mention it here because it is important for the machine to be set up well for the precise work needed to make moulds this way.
The dial indicator ‘zeroed out’. Assuming the table is flat the tips of the three screws and the tip of the dial indicator together agree to define a plane. The beam can be moved around to check alignment since the spring loaded tip of the indicator will move up or down, measuring differences in thousandths of an inch.
Moving the beam along the in-feed table shows variation from parallel of the out-feed table. Here it registers zero at the front edge of the out-feed table.
Here the indicator registers zero at about the middle of the out-feed table. This is as far as it can go without having a screw drop off the edge. (The pencil mark indicates the location of the two middle ‘feet’). The weight keeps the three screw feet contacting the surface of the in-feed table. By referencing the flatness of the longest table the dial indicator can measure deviation over about half that length.
The jointer knife honing jig that relies on my ‘mag-chuck’. The roller is the core of a defunct printmaking brayer that I found in my scrap box. I carefully drilled the two pieces of angle iron so the roller is held parallel with the flat surface of the magnetic chuck. It is also important that both ends of the roller are set back exactly the same distance from the front ends of the angle irons. These bump up against a piece of rod which in turn rests against the back of the jointer knife being honed. Everything is locked into place when the lever actuates the strong magnets in the chuck. This establishes a honing angle which can later be altered slightly by inserting different sizes of rod. In place above and below is a piece of 3/16″ diameter threaded rod which defines the first (shallowest) honing angle.
The knife is first honed with a diamond plate.
The results of using the diamond plate.
Swinging the lever from right to left de-magnetizes the chuck. This has enabled the first rod to be replaced with a smaller (5/32″diameter) rod. This moves the roller closer to the sharp edge of the knife to establish a slightly steeper angle so this India stone can remove the ‘scratches’ left by the diamond plate, but only at the very edge.
Now an 1/8″ rod makes the angle a little steeper still so this ‘Washita’ Arkansas stone can polish the edge further.
To remove the burr the knife is placed bevel side down. The magnetic base holds the knife, a 1″ wide rule and the 5/32″ rod firmly in place so this Arkansas slip stone can polish a very shallow micro bevel on the flat side of the knife to take off the burr. Few woodworkers will have access to a magnetic chuck. But I thought it deserved mention since it works so well.
A simple home-made dial indicator fixture which I use all the time. Three screws on the bottom establish a plane. A dial indicator mounted at one end measures vertically and one mounted at the other end measures horizontally in thousandths of inches. A magnet helps hold the fixture in place. I often place a weight on the top of the tool for this purpose, too.
The dial indicator is zeroed out on the out-feed table.
Then it can be moved over to set the knives at the same level.
Wood usually contains internal stresses. If the trunk of a tree grows at an angle ‘reaction wood’ will develop on the bottom or top to strengthen the tree. A windstorm may damage a tree causing different growth patterns, introducing internal tensions. Improperly drying wood can also introduce stresses. None of these are good for woodworkers. Most are not apparent until you begin to work with the wood. When it is sawed into narrower widths the release of internal tensions will usually cause wood to change shape. Sometimes this is very slight as shown above. If you are very lucky there is no discernible stress and the wood will hardly change at all.
This wood, originally from the same large plank, shows greater tensions being released. The wood I use is marketed as “Genuine Mahogany”. I don’t know the exact species. It is good for mould frames and deckles. It has little difference between tangential and radial shrinkage and swells relatively little when wet. And it is soft enough to receive brass and copper nails which is important for mould making.
Boiling wood for mould parts helps to release stresses. Lignin, the substance that binds wood fibers together, softens with heat, allowing the fibers to shift slightly. This boiling tank is made from a 4″ diameter piece of iron pipe. The bottom end is threaded and bushings are screwed in place to reduce it so that a 110 volt water heater element can be screwed in. I bring the water to a boil with the wooden parts submerged then unplug it to let it rest for an hour or so. Then I bring it back to a boil before removing the wood.
This also tests the wood. If the wood warps or twists badly it is not good for making moulds. If the wood barely changes you can be more confident that the wood will not warp or twist during the life of the paper mould. Many, many hours of work go into a mould, making it prudent to test and prepare the wood ahead of time. I prepare the frame and deckle wood in several steps. It gets boiled, allowed to dry, straightened (jointed, in woodworking parlance) and trimmed smaller. Later it is boiled and dried again and jointed and trimmed a second time. I sometimes add an extra boil for the “L” shaped deckle stock. In the process you will get a good idea how the wood will behave and with luck gain confidence in it.
This wood has been boiled and allowed to dry. Two sides of the wood are now jointed (made straight) using a power jointer. This removes any warp or twist.
A tablesaw has been used to trim the other two sides parallel with the jointed sides. Thus the wood gets a little smaller with each step. The internal tensions are gradually reduced as the wooden parts get closer to their final dimensions. The time and work actually spent preparing wood this way is not great. However you must plan ahead a few weeks to allow for drying between steps.
Deckle stock is prepared in the same way but it is shaped into a rough “L” cross section. In this photo the small scrap pieces that were sawn out remain very straight. This is a good indication that this wood is relatively stress-free.
Here, the shape of the deckle has been further refined; very close to its final shape but still slightly oversized.
This frame stock has been boiled and straightened twice. After drying out fully it will be ready for final shaping. Now the wood is still only ‘rough shaped’! To become a paper mould it will be further shaped very precisely and with very sharp tools. This will be described in future posts.
This is a plank of vertical grain Western Larch, a deciduous conifer often called Tamarack. I use this species for making ribs for moulds. I have Jim Croft to thank for this. He lives in Idaho where larch grows. He had it specially sawn for me with the growth rings in the ‘vertical’ orientation (approximately 90 degrees to the wide face). Larches can die and remain standing for many years without decaying. With the aid of my Optivisor and a pin I counted the rings. This tree was well over 300 years old when it died (the heart of the tree is not in this plank). It must have grown in a dense stand; the growth rings are miniscule. This makes great rib wood. Even with this old growth wood I use only the outer, finest grained wood for ribs. (I am spoiled). I feel a little guilty cutting it up into little pieces. Before Jim provided larch I would comb through stacks of clear white pine at my local lumber yard looking for perfect boards.
This tree only gained about 1/32″ to 1/16″ in diameter per year! As a result of growing so slowly and in a dense stand this wood has practically no internal stress.
It is easy to see if a vertical grain plank has been sawn parallel to the growth rings. It is harder to tell if it has been sawn parallel to the trunk in the other orientation. Here I have split a scrap of the plank and found grain ‘run-out’. This is best avoided for delicate paper mould ribs. I will re-saw narrow sections of this plank to eliminate the run-out before sawing out the tapered ribs.
Here the wood has been re-sawn to eliminate the run-out. This piece had a crack that shows the orientation of the grain. I drew a line to accentuate this. The cracked part won’t be used for ribs; there is solid wood on the other side and the other blanks had no cracks.
The prepared blanks are sawn into tapered rib shaped pieces. I cut these pretty close to final dimension since the wood is so stable.
Rib stock for a couple of moulds. In Britain these are called bars but I have always called them ribs.
Rib stock only gets boiled once, just to test for warp and twist. This wood turned out great. After boiling I stack the pieces so that air can circulate all around.