MOUNTING, PRESSING AND GLUING

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by Paul Armstrong

At the last meeting, I butted in as is my habit, on a conversation between John Sedgwick and Janet Trimble. It seems that Janet was having trouble with a marquetry assembly buckling and taking on awful shapes. This is usually due to the fact that different woods absorb or release moisture from the air at different rates, and wood expands or contracts vastly more across the grain than along it.

I once made a 50" round, 2" thick maple butcher block table which became nearly oval every summer - great for those extra guests that drop in unannounced. Marquetry, however, because of the large number of odd grained pieces and types of wood, is particularly prone to buckling and cupping.

Janet's solution was two pieces of plywood with the marquetry between and a heavy weight on top. This didn't work well for a simple reason: A one hundred pound weight might seem like a lot, but if it is spread over a 20 inch square piece of plywood, that amounts to only 4 ounces per square inch - not very much, and wood can have more tension than that. Conversely, a one hundred pound woman wearing spike heels, or Tim Curry, if you're a die-hard Rocky Horror fan, can exert as much as 1600 pounds per square inch on a ¼" square heel dimension.

So where is all this leading? My suggestion, as ever, practical, was to park one's car on the top of the plywood. It was soon pointed out to me that cars have uses other than marquetarian, but I used to drive a Ford van and as vehicles go, it made a better clamp.

My next idea was to actually begin and finish a picture in the same season, thus keeping the atmospheric conditions more uniform. When the laughter died down, John had a better suggestion: Using the same plywood (¾" thick is best), place a pair of hinges along one edge forming an envelope, then use one clamp at the opposite end to pull the assembly together, once your picture has been placed inside. Because there was no allowance made for any thickness between the sheets, the extra veneer thickness adds a good deal of tension on the hinge and with the clamp and leverage working for you, the pressure is ample to keep the veneer flat indefinitely.

For veneers already buckled, not just marquetry pictures, but burls and crotches as well, mist over them with water in a plant sprayer or clean 'Windex' bottle, place them between a few sheets of newspaper (brown kraft paper is better) and place - but do not clamp in the plywood press. Allow a couple of hours for the moisture to penetrate and soften the wood, then apply pressure. A crunching sound means too soon or not enough moisture.

For those of you who may remember the oval mahogany drop leaf table, I brought in last summer, for which John (Sedgwick) did an impressive job of marquetry, there was an oval flower petal design in the centre measuring about 11 by 7 inches. It was flat when I received it, but by the time I got around to using it, it had become a very pretty, exquisitely crafted salad bowl. ( I rarely follow my own advice, and I should have known better). The centre of the flower pattern was a good inch and a half up from the petals. To press this would have been to invite disaster and bring the curs of the Sedgwicks down upon my head, especially with a glue, at 200 degrees F. and 300 psi. The solution was simple, however. Using my spray bottle, I misted only the outside edges of the oval, on both sides, damper on the edge, less damp, to dry in the centre. Miraculously, as the wood gained moisture and expanded, only on the outside, the whole thing flattened out to nearly perfect condition in the space of an hour. Five minutes in the press, and twelve Hail Mary's later, I took it out, and it was virtually perfect, which proves my point that a good craftsperson is one who can hide mistakes better than everyone else.

One final note - Those of you who saw the video on marquetry on PBS, or at the meeting, using a piece of railroad track as sufficient weight to clamp a marquetry assembly in place only works well if the locomotive is included - which brings us back full circle to my original idea.

(Paul is a professional cabinet-maker specializing in custom-made period pieces, replete with inlay/overlay. - Ed.)

by Carol Teal

from Canadian Marquetry Feb 1986

The following is the procedure I use to mount all my marquetry pictures and have found it to be a very good one.

1. Square picture and choose the frame width, stringers, etc. Cut board to the overall dimensions.
2. Bond back and edges. The formula for the order in which this is done, is "BEST" – Back, Edges (top and Bottom), Sides (done after ends so the end grain on top and bottom edge strips won’t show) and last Top (the picture face).
3. Lay top or face of picture. Centre picture on board and draw pencil line around it, or measure in from board edge the frame and stringer width and draw lines accordingly. Lay picture on the board to recheck. Make sure you can see all four lines at picture edges.
4. Apply contact adhesive to picture back and board according to manufacture’s directions, extending the adhesive ¼ to ½ inch beyond the lines on the board.
5. When adhesive is ready for bonding, cover board with a slip-sheet of waxed paper leaving only top line uncovered. Carefully lay picture, lining it up with all lines and allowing it to adhere to the top line. Gradually remove the slip-sheet and bond picture to the board, smoothing it from the centre outward.
6. Now put masking tape on the edge of the picture and re-apply glue to the stringer area on the board. The tape keeps excess glue off the picture face. Also apply glue to the stringers.
7. When the glue is set, put a small piece of waxed paper over the picture and board at each corner where the stringer mitre will be. The waxed paper squares are 1 or 2 inches square. Apply stringers to picture edges, allowing only a small part of the stringer to contact the board at one time. This is done by slightly bending stringers (holding one end up slightly) so they come in contact with the board slowly, or you can use a slip-sheet here as well. Make sure to get stringer tight to the picture as you apply it. Push it tight with blunt handle of craft knife or other tool. When all stringers are down cut mitre with knife where the lines intersect. Now the purpose of the waxed paper becomes clear. You need to remove the cut-off scraps of the stringers. If scraps stick to stringer borders, just carefully remove them with a craft knife blade. Then remove waxed paper pieces and press down stringer corners.

Frame strips are applied in the same fashion as the stringer strips using the waxed paper squares on the corners of the board to prevent premature bonding before mitres are cut.

1. Cut oversize border or frame strips. Only one side of these must be straight and the outer edge need not be parallel as it will be cut away.
2. Apply glue to oversize frame strips. Cover stringers (or edge of picture if not using stringers) with masking tape to protect from excess glue and apply glue to board.
3. Place waxed paper squares to cover corners where strips will overlap.
4. Slowly apply frame strips to edge of picture (or stringer edge) pushing strips tight to picture edge as you go. Overlap in an under-over manner. You can adjust which side is over which, for cutting handedness.
5. Now turn picture face down on worktable and trim off excess frame veneers. (edge of frame is now flush with board edge.)
6. Turn face up, and using a straight edge, cut mitres from inner corner of frame to outer corner of board. Hold knife at a slight angle away from centre of body (right-handed person angles knife handle toward right side slightly.)
7. Carefully remove excess frame veneer from mitred corners. The waxed paper squares prevent scraps from bonding with the board. Using a flat square-ended knife blade, gently lift corners of frame to remove the cut-off end pieces. They will be stuck to the under side of the frame at some points, but since the contact cement is only on one side of this union, it is not a complete bond and the pieces are easily removed by slipping the knife blade carefully between the veneers.
8. Once scraps are out, remove waxed paper squares and press corners to the board with a veneer roller. If glue loses its power to contact, just heat the corner with an iron to reactivate it after mitre has been cut. Roll down with veneer roller.

Using this method, the mitres should always be perfect to the board corners.

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