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I am getting ready to assemble a dresser I've been working on and can't decide what, if anything, to spray finish on before assembly. I'm mostly just considering the two side assemblies. It's a Stickley dresser and the sides each have a small upper panel and a larger bottom panel. Because I resawed them by hand, the panels vary between 1/4 and 3/8 thick with the insides (obviously) being somewhat rough. I should also mention that the panels have very shallow groves plowed in them to accommodate drawer slides and the web frames. The rails and stiles are all 3/4 in thick.
I've always been under the impression that you are supposed to seal/spray both sides of a panel so the effects of humidity changes happen uniformly, as opposed to a sealed side resisting humidity and unfinished side suffering the ebb and flow of seasonal changes. This eventually leads to the panel cupping. My big question is whether or not a 10 in wide panel, captured in 3/4 in think material will suffer ill effects if it's only finished on the outside?
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Your concern about unbalanced moisture response to changes in RH is absolutely logical. But for whatever reason it doesn't seem to result in problems. If you look at old dressers the insides are never finished. But there's no harm in spraying the inside with a coat of shellac. I really doubt you'd have a problem with panels only 10" wide but the time it takes to give them a coat of shellac is incidental so why not.
John
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Even though it is sometimes more work to finish the inside after assembly, I prefer to do it that way. Otherwise, you have to go to the time and trouble to protect surfaces to be glued from the finish. I know some will say that it is not necessary to finish the interiors and a lot of furniture pieces have survived many years without it, I prefer to do it, but not before assembly.
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I'm very much in the camp of what John said. But I looked in Flexner's book to see what was there. He calls finishing both sides to reduce/prevent warping a myth, although it will slow it somewhat. He goes on to say that moisture vapor will work it's way through the finish and cause the same degree of any warping that's going to occur. But if it gives you some comfort, there's not all that much effort involved. Just don't put an oil based finish on the inside.
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I used to finish drawer interiors with shellac or lacquer because they both dried so quickly. But in the enclosed space of a drawer, I found that the odor remained for a very long time. Now I use a waterborne acrylic. It dries fairly quickly and no residual odor.
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To be clear, I would rather not take the time to prefinsh the insides for the reasons that Willyou mentioned. each side has 7 groves each that I would have to protect from finish as well as all the mortises. I'm feeling good about the building consensus here that it's not required.
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(08-25-2021, 07:32 AM)Cooler Wrote: I used to finish drawer interiors with shellac or lacquer because they both dried so quickly. But in the enclosed space of a drawer, I found that the odor remained for a very long time. Now I use a waterborne acrylic. It dries fairly quickly and no residual odor.
Well it depends upon which WB you use. EnduroVar (at least the original; it's now been reformulated) will stink for a long time, much longer than shellac. But if you stick with WB that have no oil modifiers (GF's High Performance or Enduro Clear Poly, for example) there should be little residual odor. I use Enduro Clear Poly most of the time and it has very low odor.
John
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(08-25-2021, 09:29 AM)mr_skittle Wrote: To be clear, I would rather not take the time to prefinsh the insides for the reasons that Willyou mentioned. each side has 7 groves each that I would have to protect from finish as well as all the mortises. I'm feeling good about the building consensus here that it's not required.
Proceed without worry!
John
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Well, the job is done and I ended up waiting until after assembly to spray the interior. Based on the input I got here, I wasn't worried about a perfect, built-up finish so I just did my best to give it a modest seal coat. I was more than happy to do the quick and easy job on the inside because the outside of the case was plenty of work all by itself with a coat of BLO, two coats of dewaxed shellac, and two coats of lacquer to finish it off. Oh and a third coat of lacquer on the top for good measure.
