What furniture parts should be left unfinished?

[David Howell]

The curio cabinet project I just finished is ready for stain and a topcoat. My question is, should every surface on it have the stain and topcoat applied to it? Or should the back and undersides, for example, be left alone?

In the dusty archives of my brain, I remember reading or hearing that the backs of furniture, insides of drawings, etc. should be left unfinished. I just asked a guy at Woodcraft and he said to apply finish (both stain and topcoat) EVERYWHERE. Is my memory flawed or outdated?

All the finishing books I've browsed through don't mention this at all.

The cabinet is all walnut. The back panels are walnut plywood. I can upload a photo if that helps.

-Dave

[David Howell]

Ok, here's an example: in a FWW article about finishing, the author (Jeff Jewitt) writes, "If you must put a finish on the inside of cabinets and drawers, use only shellac or lacquer, if possible, because oil and oil-based varnishes take a long time to cure thoroughly."

[Jamie Buxton]

Usually furniture outsides get finish. Parts that aren't seen usually don't get finish. This includes: backs; the inside of bureaus; and undersides. There's no real downside to putting finish on them, but no observable benefit. There's a common recommendation that varnish not be used on the interiors of furniture which closes, drawers in particular. Shellac, or no finish at all, is generally recommended for those places. (However, I have to say that I have varnished drawers and cabinet interiors for decades, and have not noticed issues.)

[David Howell]

Thanks, Jamie. Makes sense to me. When I think about the pieces of furniture I've encountered, those areas you describe have no stain/shellac or anything on them. The comment by the Woodcraft guy kind of threw me off.

Another comment in a Popular Woodworking article said that you should stain/finish panels or table tops on both sides so moisture won't affect one side of the wood to a different degree causing warpage. But I'm not sure what to think of that either, aren't the undersides of (dining room) tables unfinished?

Seems like this topic isn't covered in finishing articles/books/videos. Maybe it's plain to see for everyone but me.

[Chris Friesen]

Another comment in a Popular Woodworking article said that you should stain/finish panels or table tops on both sides so moisture won't affect one side of the wood to a different degree causing warpage. But I'm not sure what to think of that either, aren't the undersides of (dining room) tables unfinished?

Often commercial tables are unfinished on the bottom. This is probably not ideal for the reasons you indicate. I've seen panels finished only on one side warp when exposed to a humidity change, then gradually straighten out as the humidity permeates the wood.

[John Timberlake]

For tops, sides, backs and fronts of cabinets, I use the same finish on both sides (or very close). The back does not need as much finish if it not going to be seen, but should still be the same on both sides. For drawer sides, backs, bottoms is put a thin coat of blond shellac and then wax. The bottom of drawer runners (assuming metal slides) get extra wax. Others methods may work, but mine has worked for me. Too many old pieces have cracked sides and tops because they did not finish the inside.

[David Howell]

Thank you for all the valuable feedback. To add closure to this question for me, I'd like to include a couple of quotes I've come across since originally asking. From Taunton's Complete Illustrated Guide to Finishing (Jeff Jewitt):

"Solid wood tops, doors, and other surfaces that aren't rigidly held in place should be finished on both sides. This prevents the possibility of warping and cupping during an abrupt change in humidity."

"Never apply any finish made with a drying oil to the insides of drawers, chests, or armoires where food or clothes will be stored. This includes all oils, varnishes, modified oils, and oil/varnish blends. The smell of the product seems to linger forever. It's better to use shellac or lacquer. Reactive two-component finishes are also fine."

[Howard Acheson]

The rule of many finishers is to fully finish any surface that can be seen. Smooth and put one coat of finish on any surface that can only be felt (bottom edge of table outside the apron. No finish on a surface that can't and won't be seen.

The only caveat is if you have a large panel that is not fully supported across the grain (such as a trestle table) finish both sides equally. Supported panels do not need to be finished.

That said, it's your project. If you feel better finishing everything, go ahead.