Concertina

Wonky Laminates

So, as I wrote some time ago, I decided to make the boards for the new ends I am going to make for my concertina by laminating together six layers of horribly expensive Indian rosewood veneer. I had hoped that by now they would be fully dried and ready for me to start on the fretwork. Unfortunately they warped as they dried out. To cut a very long story short:

  • I have been convinced that they are probably too warped to use as they are. Particularly as they have warped in two planes in opposite directions.
  • They are glued together with hide glue, so in the worst case I should be able to soak them apart and try again.
  • I have a few theories as to what went wrong. My main one is that the wood got very wet and expanded during the gluing process, then the glue set so the layers could no longer move relative to each other, then the layers continued to dry and shrink over the next several weeks at different rates in two different directions (because alternate layers are laid at 90 degrees to each other for strength), setting up internal stresses in the boards that could only be relieved by taking on a curved shape.
  • Before taking the fairly drastic step of dismantling the boards, I want to try de-stressing and flattening them. For this to work I think I will have to re-activate the glue by applying gentle moisture and heat, and then clamp them flat in a press until they are fully dry, without getting the wood so wet in the process that it builds up internal stresses and warps again. I'm still pondering the best way achieve this.

Comments

Sounds tricky. Will the inner layers of laminate really dry out in a press?

How fine is the line between gentle moisture and wet...
To dry the boards in the press after I laminated them, I put several sheets of dry paper either side of them and changed the paper twice a day. At first the paper kept going wrinkly from the moisture it had absorbed. It stopped doing that after about a week. I'm not sure how long to leave them in the press this time; the first time round they were in there a couple of weeks, which I now suspect might not have been long enough. I could try weighing them every day until they stop losing mass (assuming my kitchen scales are precise enough to tell the difference between almost dry and properly dry).

> How fine is the line between gentle moisture and wet...

Exactly, I've been wrestling with that question myself. Not enough moisture and the glue won't re-activate when I heat it; too much and the wood will swell and warp again. I've been considering using the reverse of the drying process to moisten the wood: put them back in the press with sheets of damp paper either side of them.