Why did wooden furniture parts warp after staining but before assembly?

Question

I'm not sure what I did wrong. I'm building a small AV cabinet. I cut all the pieces of wood and did all the detail work (pocket holes, shelf holes, etc) first. I also let my pine wood rest before doing anything to make sure it didn't warp.

I pre-stained, stained, and applied clear gloss to one side (after waiting the proper amount of team between each).

I then flipped all my pieces over, pre-stained, stained, and applied clear gloss to the other side of all the pieces.

Now when I look at the pieces they are warped. All of them. I'm not sure what I did wrong here. Should I have assembled them together first? Before staining?

Answer 1

You're right assembly & locking into position would've likely prevented most of the warping, because Ed Beal's right. Though, longer spans would've possibly still bowed. The wood today is all new growth & very unstable compared to old growth stuff. Even tightly strapping & then heavy weighting wood together until it's dried or acclimated in a week or 2 is still far from predictable.

But after that, sanding or planing it back to reasonably flat is a better practice. Which, would be your solution at this point, for just the areas that matter most. Using Furniture Grade plywood avoids much more warping to yield better results, if you don't want to get a PhD in wood storage, curing, steaming & handling.