Can I veneer a warped panel?

[Mike Dowell]

I've vacuum veneered many panels to date, but this current project has me with a big question mark above my head. I'm replacing the veneer on a dining table. It is split in two halves, and a pretty basic leaf table - Duncan Phyfe to be exact. Anyway, I stripped the two panels down and took of all the table slides, hardware, apron, etc, so that I had basically two flat slabs. After that, I took them to a friend's cabinet shop, where he ran them through his (completely amazing) wide format drum sander. Trouble is, it's been two weeks until I could get around to the veneer step, so they've warped a bit. Both slabs have about a 1/4" warp to them, in a downwards(toward the floor as the table would be oriented) slope. I suspect this is from two reasons: 1) leaving one side not veneered, and the underside still has the balance veneer, the bottom side "pulled", thus dropping the top downwards, and 2) the bare top surface absorbed some water from the air, thus expanding, further drooping the table downwards.

Anyway, I could just go ahead and veneer these panels, but I'm scared that after I do so, and finish them, that they will straighten out, which would effectively "pinch" or "compress" the veneered top surface, and the finish. I'm concerned of the possibility that this might sort of crinkle the newly veneered top, or finish.

Is this basically a non-issue, or am I on the right track for worrying? In retrospec, I should have veneered these panels immediately after they were sanded, but I don't have a time machine, so I Can't worry about that now. I took them outside today and put them face up(so warped downward) in hopes of some direct sunlight, but the weather is not good for the next few days. I fixed a warped door that way once.

What's a guy to do?

[mike holden]

You could try laying them topside up in the sun for a few hours. They MAY flatten out, and then you quickly veneer the top. I am afraid that there will be problems if you veneer the top while warped, either the pinching you worry about, or never flattening.
Good Luck! and let us know what the outcome is.
Mike

[John TenEyck]

I would just wait a while longer. They will straighten out as the MC equalizes in them, in the same way they went wonky when the MC got unbalanced. If you can't wait, then putting a heating blanket on the side you sanded the veneer off. As that side dries it will straighten out. When you get it flat, veneer it immediately. Recognize that if you use waterbased glue to veneer it it will warp again - until the MC equalizes again.

John

[Mike Dowell]

I would just wait a while longer. They will straighten out as the MC equalizes in them, in the same way they went wonky when the MC got unbalanced. If you can't wait, then putting a heating blanket on the side you sanded the veneer off. As that side dries it will straighten out. When you get it flat, veneer it immediately. Recognize that if you use waterbased glue to veneer it it will warp again - until the MC equalizes again.

John

I use the veneer glue that is sold at veneersupplies.com - joe woodworker I think is the name of the guy. Not sure if it's water based though. So you think these planks will straighten out on their own? I hate to buy an electric blanket that I'll prbably never use again, but it is a customer job, so I can't wait too long.

[Mike Dowell]

You could try laying them topside up in the sun for a few hours. They MAY flatten out, and then you quickly veneer the top. I am afraid that there will be problems if you veneer the top while warped, either the pinching you worry about, or never flattening.
Good Luck! and let us know what the outcome is.
Mike

Yeah, just the weather is not cooperating with me here in Maryland. I will definitely be back with the outcome though.

[Robert Engel]

I'm not a veneer expert by any means but I agree with your assessment. I think the mistake was not removing all the veneer without re-veneering right away but even if you did that, it probably still would have cupped. Probably a good idea to have kept them stickered in clamps and wrapped in plastic. Happens when you're busy.

The first thing I would try is clamping the panels using cauls with the convex side up, then a fan blowing across it for maybe a day and see what you have. I would hope they should at least flatten a little, ideally all the way. But I've never had much luck reflattening a thick panel. You can also try wetting the concave side but I've had better luck with the fan method.

If that doesn't work, I would probably consider remove the veneer from the bottom and try the clamps/fan again. But that's a major PITA if using a heat gun and I don't know if drum sander would be advisable on a cupped panel.

So, if that doesn't work, I would consider x grain cleat on the underside to pull the panel back flat, then veneer the top, then remove cleat and veneer bottom.

Worst case scenario, you'll have to veneer a new substrate. Might be a viable option is shop time is limited.

[John TenEyck]

I use the veneer glue that is sold at veneersupplies.com - joe woodworker I think is the name of the guy. Not sure if it's water based though. So you think these planks will straighten out on their own? I hate to buy an electric blanket that I'll prbably never use again, but it is a customer job, so I can't wait too long.

If the panels were flat before you removed the veneer off one side, they should flatten out when the moisture that has penetrated on that side comes to equilibrium everywhere in the panels. You can just wait for the moisture to diffuse through the panels, or you can dry out the wet side; the result will be the same. If you use WB glue (yes, the stuff from Joe Woodworker is WB) to apply the new veneer it will warp again - but it should flatten out after the moisture reaches equilibrium again everywhere in the panels.

FWIW, I use two electric blankets all the time with my veneering. I use Plastic Resin Glue almost exclusively for veneering my shop sawn veneer and it cures based on a time/temperature curve. At 70F it takes 13 hours to cure, at around 100 F it's down to around 5 hours, at maybe 110F it only takes 1-1/2 hours. I get two glue ups a day through the vacuum bag by using the heating blankets. And further FWIW, plastic resin glue will never creep. You can use the PVA glues on commercial veneer, but don't try it with shop sawn veneer. A customer failure proved that to me.

John

[Mike Dowell]

Excellent info. Well, I've got the panel in the sun right now. It's been in direct sunlight for 30 minutes, but hasn't correct even 1/1" yet. it's 9/16" out across the width. yikes.

**UPDATE** It IS correcting. I just checked it after posting this, and it's corrected 1/16" so far. Course, it's 4pm now. I started too late. Maybe I'll try to catch high noon tomorrow. Also, interesting about the WB glue. Right after these panels dry, they're going to be reassembled on the table IMMEDIATELY.

**UPDATE 2** - it's now been an hour and it's corrected 1/8". So, I guess I'm looking at 1/8" per hour. Going to take them in now, and start again tomorrow. I'll allow for enough time, now that I know I've still got 5/16 to go, so that should be right around 2.5 hours - math...

[Alan Lightstone]

I'll allow for enough time, now that I know I've still got 5/16 to go, so that should be right around 2.5 hours - math...

I'll bet the farm that the time required won't be a linear relationship.

[Mike Dowell]

It worked! The sun definitely straightened this out. Not sure if it was a linear time/progress relationship, but it definitely flattened out.

[Mike Dowell]

IT'S WARPED AGAIN!!!!! I haven't been able to spray this table yet, so it's been sitting about a week in the state you see above. I noticed tonight, leaving the shop that the panels are again warped in the same way they were when the veneer was off of the top. Funny thing is, I've refinished many dining tables and never noticed them warp once the finish was off the top and they too have sat before.

Should I just go ahead and spray the top of this thing on my next decent day? Then just explain to the customer that it *will* straighten out over time? How long might this take if I am asked?

[andy bessette]

"just explain to the customer that it *will* straighten out over time"

Good luck with that.

It sounds like you let the sun dry and straighten it, and then let it re-absorb moisture before sealing.