Although I’ve done a few boxes that have incorporated resawn veneers, without problems, I’m now doing my first major project, and have what looks to be a major problem.
I’m doing a dining table top that will have a total of 14 veneers, including leafs on each side of the top. The table “halves” will each have 5, and the leafs will have 2 each. The veneeres are 7 inches wide by 39 inches long, and 3/32 thick. I taped veneers together, and glued them with yellow Tite Bond to 3/4 Fin Ply. I’m doing one side at a time. The glued veneer and substrate are sandwiched between 2 pieces of 3/4 inch MDF (1 1/2 inch total) on top and bottom, 2 X4 on edge, top and bottom on 5 inch centers that are clamped on each end with long reach clamps. The clamped assembly sat for 24 hours.
Problem: Upon removing the clamps, the panel with one side veneer has warped! The warp is across the veneer grain. The glued panel which is about 36 inches wide has about a 1/2 inch bow in the center. Before I glue on the prime face veneer, I’d appreciate guidance. Will gluing the face veneer correct the warp? Should I have used MDF instead of Fin Ply for substrate? By the way, all veneers are cherry. The veneered panels will have a solid wood frame on the outside edges, and I plan to have an apron of 3 1/2-4 inches on edge underneath. I suppose that the frame and apron can secure the panel flat, but I don’t know if it’s good to force it flat.
Comments or suggestions will be greatly appreciated.
Thanks!
Dale
Replies
Dale,
You've committed the cardinal sin in veneering. You've failed to use "balanced construction." Panels veneered on only one side will always warp as yours have. You must veneer both sides, preferably at the same time. If you apply the face veneers now, the panels will straighten, but it is uncertain whether they will come back to flat.
"Balanced" means using similar, if not the same wood on both sides, the same glue andthe same amount.
It is possible to veneer thinner stock using contact glue without balanced construction without fear of warping. But your construction requires classic methods.
Rich
Rich,
Thank you for your response. My plan was to veneer both sides. I guess I thought that I would have time to veneer sides separately, at different times. My "veneer press" set up takes time, and I was concerned about "open time" of glue.
Do you think I'll be alright once I glue on face veneer? Consider the solid frame and apron?
Thanks for your help!
Dale
Dale,
In your situation, I would go ahead and quickly veneer the other side, making all due requests to whatever Diety or Dieties you deem appropriate. (My wife would advise adequate deference to the Goddess).
Good luck and keep your fingers crossed. Keep the glue-up in the press well beyond usual bonding time and after removal, keep them flat and under some pressure for several days.
Rich
Thanks!
Dale, you might also want to consider switching to a urea resin glue, such as Unibond 800, for your veneering projects. It has a relatively long open time, isn't subject to creep and/or shrinkage, holds a rigid glue line, is decently water resistant, and can be tinted using colored catalyst powders or aniline dyes (thus helping camouflage glue lines that might otherwise be visible).
I've found it very easy to mix and use -- but use a mask and gloves throughout.
DavidHmmm... the garden or the workshop today?
Thanks for your reply!
Can you recommend a source, or Brand name?
Dale
Dale,
It won't help you on this project, but for future reference, on the FWW site, do a search for "iron on veneer" and see what comes up. At least two articles have been in FWW about using yellow PVA glue as a thermal setting glue for veneering. You brush on two thinned coats to both veneer (don't forget to mist the top side) and substrate, allowing first to dry to touch before applying second, and second to dry to gloss. Then using a medium household iron set in the mid range (between wool & cotton) iron the veneer down, kinda like the iron on edge banding for plywood. Some beautiful work shown in the articles.
--
Lee in Cave Junction, Oregon
On the Redwood Highway
Dale, here's a link to Vacuum Pressing System's website:
http://www.vacupress.com/vacuumveneering.htm
I've found them to be very helpful, not only over the phone but on the online forum, etc. The prices seem reasonable, delivery is fast, and it's nice to have so many veneer-related products in one place (even if you don't use a vacuum press).
Also, Certainly Wood is a nice source for high-quality veneers as well as the cheaper veneers for counterbalancing the opposite, unseen side of a piece (forgive me, I'm drawing a total mind blank as to the correct word for this... too early, not enough coffee...). Flamingo Veneers was an old favorite, but they've gone out (or are still going out) of the veneer supply business (their custom furniture biz is going very well). Here's a link to Certainly Wood:
http://www.certainlywood.com/
DavidHmmm... the garden or the workshop today?
Go for it. If you use the same type of veneer and the same glue on the good side, I think it will flatten out. I don't think 1/2 inch bow across a 36 inch panel is too bad considering you have fairly thick veneer. Nick
Hi there,
Ditto to the iron-on technique mentioned earlier. I read the articles in FWW a few months ago and was intrigued. I gave it a shot and I can't see why anyone who isn't after the joy of doing things the old way or working on a huge project would not consider this. It's so easy and you'd avoid the complicated set-up you already mentioned that takes "Time". Here you probably could have done one side after another in as little time as it takes to flip the piece over - maybe avoiding the warp. Give it a try during your next at-bat and good luck with the table.
Erich
For what it's worth Dale, I've been veneering one side at a time in a bag press on and off for the last 25 years. My routine has always been to prepare both sets of veneer, i.e., the lesser quality balance veneer and the show veneer. Lay the balance veneer on the panel, trim the edges once the glue has set, and immediately lay up the show side to get the panel back in balance as quick as possible. Most veneered panels tend to cup a bit, and this is partially caused by the difference in strength between the two types of veneer-- often the show face is of a different species to the balance veneer, and there is, naturally, a difference in strength between the two.
In traditional work using hot hide glue and a veneer hammer you can really only veneer one face one day, and the opposite face the next, so warpage overnight is quite common. (You can veneer one face early in the morning, and the second last thing at night.) The application of the second face usually brings it all back into a fair resemblance of flat. Your veneer at a little under 2.5mm (I had to convert to get a feel for the thickness, Imperial measure not meaning much to me) is a little thicker than what is common nowadays, but it's thinner than much of what was used yonks ago, so it's quite strong with a good ability to cup the groundwork. If you've not already done so, lay the second face, and I bet your panel will straighten out considerably to acceptable levels.
Plywood, if smooth, which it often isn't, is an ideal base to lay veneer on. Plywood, especially the cheaper stuff can have a lot of surface variations in it from voids, grain type, poorly operated and dirty dimensioning sanders, and other processes, so you have to watch the stuff. Any bumps, hollows, ridges, etc., will telegraph through your veneer layer particularly if used for horizontal surfaces such as table and cabinet tops. Sometimes MDF is better for this application simply because the blemishes I mentioned aren't seen anywhere near as often. Perhaps there's more rigid quality control going on during the manufacture of MDF panels than there is with plywood panels.
One advantage of PVA glue for veneering in a press is that you do get one extra chance to repair wrinkles if they should happen. With urea formaldehide (as has been mentioned as an alternative) you get only one chance, and in years to come, repairs are harder to effect. My favourite glues for veneering indoor furniture are hide glue, followed by PVA, then urea formaldehide(sp?) Others have different preference orders. Slainte.
Sgian,
Thank you for your response.
Since my original posting, I've veneered the other side, and the cup is nearly gone, adding the solid frame and apron should give me a flat panel.
Using PVA, I assume this is yellow glue, gives you a second chance. What do you mean by this?
Thankd!
Dale
With standard contemporary veneer thicknesses being in the 0.6- 0.8 mm range at their thickest-- sorry, got to use metric here as I've no real mental grip on small fractions of an inch-- they'll sometimes wrinkle during pressing. With PVA, the second chance refers to the ability to sometimes get back at the job with a scalpel, a bit of moisture, some heat and lifting, and pressing and ironing down flat, and a bit of overlaying, and retrimming to create a near enough invisible repair. Your veneers might be a bit thick for this 'second' chance.
PVA and aliphatic glues are the yellow carpenter's glues, and in the US, the cheaper (and slower setting Elmer's white glue.) You can further slow down setting times by adding water to these glues, which also makes them easier to roll on to the groundwork, etc.. Slainte.Website
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