Many of us might be curious to know why plywood warps worse than anything else and what are ways of storing it to prevent warping?
There are some responses from Cabinetmaking Forum.
1. I’m not an expert on plywood but I know that after we installed an automatic moisturizer in our shop to keep the humidity around 35%, most of our warping problem was solved. I am amazed at the difference it makes.
2. What type of plywood are you having problems with? I have never had any major problems with warpage when using quality plywood, but even the most expensive ply can have a slight bow to it. As far as storage, if you have enough room in your shop, you should store your plywood laying flat so it won’t warp easily when you use it for projects.
3. Twist is a common type of warp with plywood. The reason is that the MC changed after manufacturing. Plywood is almost always a low MC product as the heat used in drying and gluing assures that the plywood is not wet, but rather is fairly dry. Construction plywood with warp is usually not an issue as it can be nailed or screwed flat when used for sheathing, etc. which is what it is designed for. When construction plywood is used for other uses, the warp is serious. One way to reduce the problem is to use a composite core (particleboard, MDF). Another is to use a higher grade of plywood. In any case, any attempts to reduce moisture changes will ease the warp issues. As an additional note, when using plywood, it is prudent to coat both faces with the same coating system to avoid moisture differences between the faces and warping.