I am veneering a couple doors for an armoire. I milled the the maple veneer myself to ~1/16″ thick. I edge glued 5 pieces together (they glued up nicely and sat flat, it is mostly 1/4 sawn) to make a a sheet about 16″x36″. I glued on the back panels to 1/2″ baltic birch ply using a vacuum press. First one came out pretty good the second one came out with a terrible bow to it. It is unusable.
Should I have glued both front and back veneers on at the same time? I did make sure the grain of the veneers was going at 90 degrees to the face veneer of the ply. Should I have used MDF? I am just glad I did the back first because the front veneers have many hours of marquetry on them!
thanks for any suggestions.
Replies
It is just my opinion, but I think you should have been ready to glue both sides at once. Or, worst case scenario, you should have glued the face first, then after about 1 hour, glued the back. Things balance out that way.
The big bow you experienced is because you introduced moisture into one side of the plywood and veneer.
Also, the face needs to be similar veneer to the back, and the same thickness.
You can also help thing be flat by using a flat board (like 3/4" melamine) inside your bag for everything to suck up to. It must be flat though.
Hal
http://www.rivercitywoodworks.com
I agree with the others, either veneer both side at the same time. Or use MDF or I likkke moisture resistant chipboard. Weather you like it or not, Plywood is still wood and will move on you.
http://www.kalafinefurniture.blogspot.com
You don't mention the type glue, but it must contain water.
I veneer both sides at the same time in a press. I don't necessarily use the same species nor thickness though I am certain that is the best idea for everything except the budget. I feel fairly certain that differential moisture levels in the face and back are by far the greatest problem. I have achieved almost perfectly flat panels using 1/4-inch Baltic birch ply using my methods. Your 1/2-inch ply should do even better.
If you have veneer to spare, you might try veneering the back of your warped piece. It probably needs to be clamped up very flat between cauls as the glue sets. A vacuum bag may not clamp with enought force to flatten it. Good luck!!
Cadiddlehopper
twodot, You must always veneer both sides of the substrate, unless you are using contact cement (solvent-based, not water-based). Veneer the back of the warped piece. First wet the back and it will start to flatten, then veneer it and clamp it flat. Keep it clamped for at least 24-48 hours. Then let it settle down. It will probably stay flat. You also need to veneer the back of the panel that did not warp (yet). Rich
Thank you all for the info. I should have known better and veneered both faces at the same time. So now I am faced with the dilema of either gluing on the face veneers (with hours of marquetry on them) and hoping things equal out flat or scraping these and making new ones and this time gluing on both front and back veneers at the same time. I assume MDF would have done the same thing if I had glued on only one veneer at a time??
"I assume MDF would have done the same thing if I had glued on only one veneer at a time??"
Yes. "Balanced construction" is always required, except if using solvent-based contact cement with thin veneer.
Rich
First of all I think that a vacum press is going to put way more force on the board than a caul and some clamps ever will. I alway place my veneer work inbetween two calls and then put it into the vacum press.Secondly, I don't think that MDF is going to have the same problem. Of course that depends on the thickkness of the MDF. The main problem I would see with MDF is that it might delaminate. Unlike Chipboard, MDF has a tendency to peel off in layers.Kaleo
http://www.kalafinefurniture.blogspot.com
"I think that a vacum press is going to put way more force on the board than a caul and some clamps ever will."I think that you should try to prove this supposition. The result may surprise you.Cadiddlehopper
Caddidlehopper,
I, like you, use a cold press or clamps and cauls when veneering. The results are always good. I never tried a vacuum press.
I can see a vacuum press being useful when gluing veneers to a radius, but even there, I have done that sometimes and even made curved veneered doors. I build matching curves using particle board to use as a caul when gluing up the doors or curves.
I guess I am a traditionalist when it comes to woodworking technique. I suspect that you are also. JL
I hate to disappoint, but traditional I am not. I would say I am pragmatic. If I think it will work for me, I might try it. In a previous life I was a design engineer with a capital DESIGN. That is what I really feel compelled to do. I still hold the mortise & tenon and dovetail in high regard, however. On the other hand, I have some creations in the style of Wendell Castle. My primary requirement for a project is that I have some fun with it. Thanxx!! for the interest.Have you thought about using sandbags for mild curves? I recently bent a heated mica sheet that way. Never tried veneer. I suspect that a vacuum press is superior. Cadiddlehopper
Cadidd,
Sandbags?..heated or cold?..if they are to be used as the form, how to keep them from changing their shape?(would I need to create a particle board form to have the same sit against and to receive the clamps?) This is an intriguing thought non the less. I can see heated sand as a way to prepare the wood for bending, the rest is still a bit vague, as you can see.
I did not mean to insult you by calling you a traditionalist :-), though coming from me it is meant as a compliment. I too am prepared to look at different solutions with an open mind, but I seem to be able to solve my puzzles the great majority of the time using techniques that I learned a 'while' ago. Mind you, maybe some of those techniques were not traditional at the time, but they did become part of my tradition.
I enjoy reading your comments in all the forums. You are soft spoken, but get right to the heart of the matter. JL
I was not insulted. Traditionalist is a neutral word just like warlord. The guy can be beneveolent or otherwise. But thanxx!! for the compliment.Sandbags can be used as weights to press (whatever you want) to a form of some kind. I heated mica sheet material, laid it on a form, then laid a sandbag on the mica. The cold sand cooled the heated mica quickly. You are limited by how large of a bag you can handle in the process.Cadiddlehopper
A primary benefit of using a vacuum press is the uniformity of the force applied. Cauls and clamps may result in greater local pressure but that will decrease in the areas not directly under a caul or clamp. One must make sure the system is designed properly to give adequate pressure. The vac system gives about 15 psi over the entire surface.
We both seem to understand what you said. Indeed!Cadiddlehopper
A vacuum press put up to 9 tons of pressure per square meter. Which from what I have read is a about what you get from a mechanical veneer press. Although I will admit that they say that a mechanical press does provide more pressure. With that said, they are talkking about a professional mechanical press and not just a couple of cauls and some bench clamps. I still don't think that you can get 9 tons of pressure per square meter with a caul and some clamps. Plus with a vacuum press it is constant and equal pressure from all sides and in every spot of whatever you are veneering. A caul might deliever the pressure from the clamps, but never in equally over an entire surface.Please don't get me wrong, I do use cauls and clamps. But I also use the vacuum press for all my veneering.Kaleo
http://www.kalafinefurniture.blogspot.com
Being a dyed-in-the-wool skeptic, I have my doubts that a vacuum press will flatten a warped board of appreciable thickness because the pressure of ~15 psi distributed evenly. I suspect that local pressures much higher than that are required for flattening it. An experiment is in order. I have no vacuum press, so you must do it if it must be done. It may work, but I doubt it.I have no idea how much pressure my press applies. I have broken parts by cranking it too hard.Cadiddlehopper
Cadiddlehopper,
I tend to agree with you here. When wood is warped a press may flatten it while it is in the press, if it doesn't outright break it, but once removed it will return to the warped state.
I have had some luck in restoring warped panels by placing the panel with the high spot up on a humid surface and applying a gentle weight applied to push downwards. In about 24 hours or even less some of the pieces flattened out, but not all. JL
"some of the pieces flattened out, but not all."That is why I suggested trying to salvage a warped panel only if there was veneer to spare.Cadid
I have a question...
I've never done veneering before but know that I will some day. Is this warping problem there if one was to use a solid wood substrate?
I spent a fortune on deodorant until I finally realized that people didn't like me anyway.
ChuckN,
The veneer that is available on the market today is too thin to be used properly on a solid wood substrate. Classic top of the line furniture built during the last couple of centuries was almost always veneered, on solid wood substrates, using hot hide glue. The veneer was applied by rubbing... but the veneer was thick, really more like thin pieces of solid wood rather than paper thin slices of veneer. (this to paint a picture. I know that veneer is thin, very thin, solid wood)
If you do not want to use particle board core or MDF as a substrate, there is always solid core plywood for producing panels. I have sometimes veneered solid wood, but it always feels wrong when I do it and it is usually to please a client that wants a look that is too expensive to produce in solids, but you would then need to use a solid wood with very little grain pattern to reduce the problems you will run into when the substrate starts to expand and contract.
As some of the previous posts showed, you need to balance the work by applying a backing sheet if you are gluing up parts for machining and assembly. It is not absolutely necessary to use the same species of veneer but it is always better. If you purchase your veneer in flitches, consecutive cut bundles as you move through the log, you will have plenty of sapwood and less appealing pieces available so that you can use the same species, otherwise, use a similar type of veneer. It will still work. If the piece you are veneering is a cabinet and it is already assembled and therefore 'locked', then just apply to the face (you don't actually have another choice at this point). JL
Edited 1/6/2007 1:20 pm ET by jeanlou
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