This question was asked by Mike:
I plan on building a small box for my daughter’s birthday, and I want to use a veneered panel for the lid. I plan also to use PVA, and a press as the lid will be small (5×8) and I don’t think it needs any more. When watching you make Nicole’s frame, I noticed that you veneered both sides of the frame even though only one would show. Is this to ensure that the moisture balance in the piece stays equal, or was it just pride in craftsmanship? Also, if you’re veneering plywood or MDF, is this necessary considering that these materials are dimensionally stable?
As always, keep up the good work – you’re definitely my reason for trying my hand at fine wood working. Thanks!
And this was my response:
Hey Mike. In most woodworking circles, it is believed that you should always veneer both sides of a panel. By adding a layer of glue and a thin sheet of wood, one side of the panel will absorb and lose moisture at a different rate than the other. This lack of “balance” could lead to warping. If you ever have a sheet of commercial veneer laying around, you can see exactly how this works by applying a little water to one side of the veneer. It will curl up like Pringles chip (pic 1)! The side that receives the moisture expands, and the other side does not, resulting in a severe curl. Wet the other side (pic 2) and the sheet relaxes once again (pic3).
When we’re talking about veneer on a substrate under normal conditions, this effect is not nearly as great. Furthermore, I have seen the rule of thumb broken a number of times with no detrimental effect. But with my projects, most times, I don’t take the chance. I like to play it safe and usually veneer both sides. And again, this is really a “better safe than sorry” type of thing. Perhaps one day I’ll do a bunch of test panels and see what really happens. Good luck Mike!