Should I finish both sides of a reclaimed Douglas fir dining table?

[Steve Van Kirk]

Hi folks,

First post, so go easy on me.

I'm building a dining table for my wife out reclaimed Douglas fir structural timbers. The wood is over 100 years old and has tons of "character" - knots (filled w/epoxy), nail holes, small splits/cracks, powder-post beetle tunnels, etc.. "Rustic elegant" is what we're going for. The top is made from four individual planks that are approximately 10-11" wide by 7' long by 1.5" thick. It is not glued up as a single panel. The planks were intentionally not milled to perfection (e.g. don't have uniform thickness, not planed perfectly flat, etc.). When you run your hand over them, you'll notice the areas that were sanded deeper out of necessity. This was intentional & was part of the overall look & feel we wanted.

The construction & finish-prep is 99% complete. Within a few days I'll be ready to start applying finish. I have chosen Waterlox. I'll be using the original sealer for the first coats & ending with a couple coats or so of the satin.

So leading up to my question: my wife and I like the idea of leaving the underside of the table unfinished so that people who dine with us can sign it. I'm a little uneasy about this, however, because I've read that if you don't finish all sides of a board equally, you can get have problems. Moisture will affect faces of the board unequally during seasonal changes, so cupping, etc. may occur. Yet the table we currently have is unfinished underneath and we've never had any trouble.

So my question is this: should I finish all sides of the table-top planks, or is it safe to leave the underside unfinished?

FWIW, I live in the Pacific NW. The seasonal moisture maps I've seen show that the variation for indoor woodwork isn't as large as other parts of the country.

Thanks for the help!

Steve

[Prashun Patel]

I would finish the underside as well. You can at least seal the bottom with the OSF - you don't need to go all the way to the satin down there. You will probably still be able to sign it if you don't build to a thick film. The signatures may, though wipe off relatively easily (unintentionally) depending on the ink you choose. You may therefore get a little spray can of shellac and give the signature a thin coat in order to seal the signature in a little better.

[glenn bradley]

I finish both sides of any large panel. For enclosed items like chests I use shellac on the inside to avoid odor problems, for tables I use the same finish on both sides for simplicity.

[John TenEyck]

I'd put one or two coats on the bottom sides and call it good. Give your guests a permanent magic marker to use to sign it. As you said, lots of furniture, including a bunch I've built, was only finished on one side with no adverse effects.

John

[Steve Van Kirk]

Hi guys,

Just wanted to stop back & say thanks for the advice. I decided to finish the underside with a couple coats or so. Just finished putting the 2nd coat on.

Thanks again!


Steve

[John Goodin]

I am building a similar sized and styled table out of maple boxcar flooring and plan on finishing both sides the same. The risk of distortion is too great. I wonder if finishing the bottom and then scuffing it up with some 220 or 320 would allow a sharpie marker to stick. Maybe not finish the inside of the apron and allow people to sign there.