Wcndave Posted November 21, 2011 Report Share Posted November 21, 2011 Anyone using solidwood has to dedicate most of their design and processing to allowing for movement. However what about veneers? let's say I have 6mm ply and put on a 2m veneer, and it's 90cm across? I assume the glue simply prevents it, however the wood wants to go somewhere, would you not expect cracks, or a bend in the entire piece. I never really thought of it before, however it came to make after watching Marcs episode "wish you veneer"... Quote Link to comment Share on other sites More sharing options...
dwacker Posted November 21, 2011 Report Share Posted November 21, 2011 Thats why you use a backer veneer. Don Quote Link to comment Share on other sites More sharing options...
areynoldsre Posted November 21, 2011 Report Share Posted November 21, 2011 Once dry a wood veneer isn't going to move. Veneer over ply won't move once the glue is dry and you don't get it wet. I've seen the gluing process bend thin sub-straights - especially thin plywoods so it's important to keep the glue up flat and in clamps for at least an hour. Also when using thin bases I always put a veneer on both sides that way the any bending will cancel out. for veneering I prefer to use MDF as a base - it's more stable and often cheaper than plywoods. Quote Link to comment Share on other sites More sharing options...
Beechwood Chip Posted November 21, 2011 Report Share Posted November 21, 2011 Think of it this way - if you glue a veneer to a sheet of plywood, you've just added one more ply to the plywood. Each layer of the plywood is a veneer. If the plywood wasn't going to move before, then it's not going to move after you add one more layer. Quote Link to comment Share on other sites More sharing options...
Wcndave Posted November 21, 2011 Author Report Share Posted November 21, 2011 Think of it this way - if you glue a veneer to a sheet of plywood, you've just added one more ply to the plywood. Each layer of the plywood is a veneer. If the plywood wasn't going to move before, then it's not going to move after you add one more layer. Well, veneer on one side might cause bend, however the idea to do both sides might work. seems a shame to do so when you are using expensive woods to veneer and won't see it. Also, ply has each layer done at right angles, whereas one would not necessarily be following that path... so you may find movement could occur. Really it seems unlikely to me to be much of a problem, however not done it before, so i wanted to check if there might be any splitting/cracking. thanks for your help guys! Quote Link to comment Share on other sites More sharing options...
dwacker Posted November 21, 2011 Report Share Posted November 21, 2011 Thats why they are called backer veneers. You use the cheapo stuff on the back Quote Link to comment Share on other sites More sharing options...
areynoldsre Posted November 21, 2011 Report Share Posted November 21, 2011 Thats why they are called backer veneers. You use the cheapo stuff on the back so true - if you do any amount of veneering you'll find that you have a box full of extras that you don't know what to do with. Mine go on the back. Quote Link to comment Share on other sites More sharing options...
Wcndave Posted November 22, 2011 Author Report Share Posted November 22, 2011 That's what backer veneer meant.. ok.. makes sense now (I thought some special backing or glue or something at first, sorry, being dense...) Thanks! Quote Link to comment Share on other sites More sharing options...
paoloberno Posted November 22, 2011 Report Share Posted November 22, 2011 Veneers made of solid wood are definetly going to move, if you are veneering a thin panel both faces must be veneered with the same grain orientation, obviously if you are using a thick panel (or a torsion box) and a thin veneer (i.e. 0.6mm veneer on 20mm plywood) you can go with only 1 veneered face... Another problem may be cracking, very wide veneer sheets glued with pva glue (or other water based glues) will absorb water from the glue and crack upon drying, to solve this avoid water based glues or strip the veneer in narrower stripes (i suggest the first)... Quote Link to comment Share on other sites More sharing options...
Wcndave Posted November 24, 2011 Author Report Share Posted November 24, 2011 Thanks, what do think about 4mm veneer on 19mm ply? Also, I only really use white glue, is that the pva one? What other glues would be recommend for wood? Quote Link to comment Share on other sites More sharing options...
paoloberno Posted November 24, 2011 Report Share Posted November 24, 2011 A 4mm veneer is very thick, i have no experience but i think that 19mm ply should be rigid enough (better if you use plywood made with a high number of plies) to resist bending... I don't know exactly the english names but white glue should be pva based, for very wide veneers i would prefer a contact adhesive, i forgot to mention that contact adhesives are better also for thin veneers of coarse grain wood (red oak but i had problems also with sapelli) since pva glue can pass trough the veneer causing problems when finishing... Quote Link to comment Share on other sites More sharing options...
dwacker Posted November 28, 2011 Report Share Posted November 28, 2011 Veneers come in many different varieties. Thick shop made, thin factory made, wood backed, paper backed, phenolic back you get the point. Glues white glue, yellow glue and so on have become generic terms and should not be used generically especially with veneers. Wood moves that's just the way it is, some more than others. In terms of veneering the more a wood is likely to move the harder the glue should be. Thick shop made veneers are going to move a bunch so contact adhesive would be the worse possible choice but phenolic backed don't move at all and contact adhesive works well in a production environment. Most home shops don't keep a supply of different glues for different applications it would just go bad sitting on a shelf. You generally turn to what you have on hand which is usually pva white or yellow. These vary by brand so you have to understand your glue of choice. Elmers white is usually thin and slow setting and would not make a good glue for thin sheets but is fine for thick shop made veneers. Yellow is thicker and sets up quicker with less bleed through so it better for thinner sheet. Wilsonart white is even thicker and sets up faster and works great for very thin full sheets and can be used every day in the shop. There are glues that are made just for veneering, cold press glues they dry very hard and are of course the best but how many home hobbiest don't want to buy a gallon of glue to glue up a small area and have it go bad on a shelf. I guess what im getting at is you need to look at your individual project and use what you have readily available within reason. If your working with shop made veneers most anything is fine except contact cement. If your working with a super thin waterfall bubinga then you probably should step it up a little and go for ultra cat ppr. Don Quote Link to comment Share on other sites More sharing options...
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