Don Stephan
Posts: 825
Joined: 2003-07-18
Location: Cincinnati, Ohio
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Here's what I have accumulated from the forum over the years:
"Veneer should be flattened whenever it is buckled, and even when seams are hard to tape because of light curling.
"Make sure that consecutive numbering of the sheets of veneer is not lost during the flattening process.
"As an alternative to a commercial flattening solution, one can mix together:
2 parts white or yellow glue
3 parts water
1 part pure glycerin (usually obtainable from a pharmacy)
1 part denatured alcohol
"One approach is to apply flattening solution to both sides of the veneer liberally. Simplest applicator is 3” or 4” foam brush. Let soak for a minute or two. Place 2-3 layers of newspaper on the table. On top of this place a layer of fiberglass window screen, the soaked veneer, another layer of fiberglass window screen, and 2-3 layers of newspaper. Continue by adding more screen, veneer, screen, newspaper, stacking as high as needed. Flip each piece of veneer end for end so the wavy parts cancel each other out. Place this "sandwich" in the vacuum press with bottom and top cauls (1/4" minimum.) and apply full vacuum pressure. Change the newspaper 3 times the first day and leave under full vacuum pressure overnight. After being in the vacuum press overnight the fiberglass window screen is no longer needed as the veneer has dried sufficiently so that it will not stick to the newspaper. Change the newspaper 3 times the second day but do not put the sandwich in the press, just place weight on top of the top caul to hold the stack down. On the third day the veneer should be ready to use. Best to confirm with a pin type moisture meter that the veneer is dry.
"As an alternative to soaking the buckled veneer with flattening solution, lightly mist on each side with flattening solution. Stand the veneer on edge out of bright sunlight, allowing air to circulate around both side, for 20 minutes. The veneer should be flexible enough to begin flattening. Flip each piece of veneer end for end so the wavy parts cancel each other out. Place the stack between cauls and gradually increase pressure until the veneer is flat. Leave for about eight hours. Then build a stack alternating a couple sheets of unprinted newspaper (or other absorbent paper) and veneer. Place this “sandwich” in the vacuum press with bottom and top cauls (1/4” minimum) and apply full vacuum pressure. Change the paper every few hours until the veneer is dry, which may take up to five changes over a few days. Best to confirm with a pin type moisture meter that the veneer is dry.
"The veneer will stay flat for months provided it is stored flat with light applied pressure. Newspaper between the sheets is no longer needed.
"Local pharmacies often carry smaller quantities of glycerin, and might be able to order gallons."
The window screen prevents the newspaper from sticking to the veneer while the solution is still "sticky."
If it's hard to align seams for taping, the veneer needs to be flattened. If there's more than just a simple curve, it probably needs to be flattened.
Think of a piece of aluminum sheet. If you hit it in the center with a hammer, even lightly, the aluminum stretches under the impact, creating a bulge. The surface area of this dented area is greater than it was before the impact, so if you try to push it back flat it simply bulges out on the other side. This is probably what is meant by the above term "buckle" - the veneer bulges out in a spot. When you have that, it's very hard if not impossible to get a nice smooth pressing without first flattening.
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