what am I doing wrong?

[kerry grubb]

I am building a repro. of the Seaton tool chest and am trying to veneer the lid of the removable till. The top is 5/8 white pine about 11 by 34. The problem that I am having is as follows. I glued on two ovals with banding on the face side of the board and it started to cup slightly and there became a good bit of wind to it. I thought at this point that I should veneer the back side as well to equal things out. After doing this the board cupped significantly.  I am using hot hide glue and home made veneers of mahogany. Not sure of the thickness of the veneer but its about 10 times that of store bought. Is there any chance of getting this flat or do I strip of the ovals and start again? Thanks for any help.

 

[Jeff L Headley]

Stand it up beside your bench. Let air get all around it for a week or so and see what it does. It could level out. 5/8 seems thick so it might take a little longer although it still should level out. Your sub structure is important also. If your boards for the sub structure move after sizing they will continue to do the same.

 

[albreed]

Kerry- I veneered one side of the base of a dwarf clock front,12 X 12X 1 1/4 thick using hide glue. The glue pulled the board about 1/8th hollow in a day or so. I waited a while to see what would happen- nothing. About a month afterwards I veneered the back, hoping it would straighten out- nothing......
I learned from this to assemble the base box of the clock before veneering. The stiffness added by joining the sides of the box to the front worked, and they now stay flat.
As we say in NE, this stuff is wicked strong.-Al

 

[ttalma]

While I don't have as much experiance as Al Or Jeff I'll toss my $.02 in.

10 times comercial thickness would make your veneer 1/4" thick, so I'll guess your exaggerating. I resaw my own veneers and I try to get them down to about 3/32 ~ 1/16 of an inch at most. Much thicker than that and you'll have problems.

I have never found veneering the backside to help. But wood selection is more important. The moisture in the glue is probably causing the warp. Try 1/4 sawn material for a backer, I usually look for this when I plan to veneer. If you use flat sawn, veneer on the bark side of the board. The wood's natural tendancy is to try to flatten out the growth rings, the moisture in the glue will cause some expansion, and the counteraction of the two seems to help a little. I would also guess you are using kiln dried wood. If you have access to some air dried wood try that.

But no matter what you do I would clamp the board to a flat surface for a few days to let it fully dry. But in the end it's wood and it's going to do what it wants, all your trying to do is make it do what you want.

 

[dkeller_nc]

Kerry - This is a bit of a long shot, but if all is lost anyway if you can't flatten the board, it's worth a try:

Dampen (but don't soak) a towel larger than the board you're trying to flatten.  Set the board down with the concave side down on the towel.  Then very gently heat the side that's up and convex with a blow dryer on the "low" setting.

The moisture on the back side will expand the wood fibers, and the blow dryer heat on the other side will dry that side out, contracting it.  It may take 30 minutes or more of careful monitoring, but the board should eventually flatten out.  Once you get it flat, it must be constrained in this shape and left to dry for at least 3 days to take the "set" that you've put into it.

I've used this several times on big, wide boards that were too thin to flatten the surface with handplanes, and it does work.  Occasionally, the board will split when in the clamps as it's drying.  I figure that's OK, because the other option would be to rip the board in two, flatten both pieces, and glue it back.  Once the board splits, I wind up having to do that anyway, so no big deal.  But many boards will flatten out, not split, and be usable.

 

[kerry grubb]

Gentlemen, Thanks for the comments. First the veneer is about 3/32.  I stood the piece up next to my bench and a dehumidifier that I keep in the shop for the summer. It tends to get fairly humid in Maryland during the summer. I let the piece sit for a week or so and the cup has worked itself out. Before I did this though, I tried putting a wet rag on top of it and put a  couple of cauls then clamped to a flat bench. This did not seem to help. The problem now is there is still a bit of winding over the length. As typical of most of my  projects I made the top last winter with breadboard edge and it sat it the shop for months perfectly flat. I am going to let it sit a while longer to see if it will flatten but I have my doubts. Will probably just start over before I get too much time involved with the veneering.