Finishing bottoms/concealed surfaces


Isaac

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I've been wondering, Is there a rule of thumb for what surfaces of a project should generally be finished? Is it as simple as just finishing the outside/exposed surfaces that are expected to be seen?

Are there any issues associated with having one side of wood boards finished and the other left untouched, in terms of absorbing moisture?

For examples: the inside surfaces of a cabinet that would only be visible when the drawers are removed, or the bottom surface of the bottom shelf of a bookshelf that rests directly above the floor. 

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I think this becomes a more important factor for solid wood projects with large parts like table tops or large panels where difference in moisture content through the wood could cause problems.  I put one coat of finish on the underside of table tops, etc.  For panel construction where there aren't any large pieces of solid wood, if think that is is less of an issue.  I have an old, old wood filing cabinet with not finish on the in inside and, because it is panel construction - it's in great shape.

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40 minutes ago, Chet K said:

I know this is one of the topics that can be all over the place but I have aways gone with the idea of getting some finish on all surfaces.  Inside and outside of all parts.  Not as many coats as the "show" parts but something.  I would hate to go through all the work on a project and then have something go wrong down the road because I didn't put finish on a surface.  In the big picture, cost wise, using some extra finish to protect the whole piece is a pretty small expense for some piece of mind.

 

Makes sense. I never even thought about the expense of the extra finish, just was wondering what was best practices. 

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2 hours ago, RichardA said:

Finish all solid wood sections as though they are going to be seen. Obviously, the unseen parts can get by with less, but they should be sealed against humidity and moisture.  If you leave one side unfinished, over time it will suck in any moisture, and cause the public surfaces to curl or seperate.

My girlfriend has been a woodburner for a while, and is very gifted in that aspect.  But her knowledge of the wood itself, and how to treat it, is severely lacking.  Most of her older works, she only applied a finish to the show side of the piece.  Now most of them are warped, mainly due to the moisture getting in one side, and not the other.    While being just a neophyte in woodworking myself, I always put at least a coat on the hidden side of pieces to help prevent this. 

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All surfaces receive some form of finish.  The exception is drawer boxes in pieces I make for myself. Pieces for others get the drawer boxes shellac'd as I don't know if they may move to another area or not.

On something like a dresser all out of sight surfaces get sprayed or padded with shellac.  Its quick to dry, retains no odor and has been adequate for balancing moisture absorption for me.

I have made some pieces made to be viewed from all sides.  An example would be a buffet that was also used as a divider to create different "spaces" in a large room.  In this case I used a frame and panel back that echoed the front door and drawer areas.

Other items that will have their backs against the wall get some love but, it is more functional than aesthetic.

 

Kit-Hut-(60).jpg

CoD back (3).jpg

Media Cabinet (66).jpg

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The way I see it you already have a brush/rag/spray gun with finish on/ in it and like Richard said at a minimum seal up all surfaces just to control moisture. I start with backs/bottoms and concealed surfaces. Then if you flip the parts a little early who cares if there is a mark or fingerprint on the underside ?

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