When and how to finish

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Forum topic by gepatino posted 11-24-2012 11:57 AM 1127 views 0 times favorited 20 replies Add to Favorites Watch
View gepatino's profile


217 posts in 2091 days

11-24-2012 11:57 AM

Topic tags/keywords: question finishing

Well, the subject doesn’t say much, my question (absolute newbie) is:

When you make something that will have a side that is not visible, how do you finish that part?

I’m talking of something like the downside of a tabletop, or the steps of a saircase.

Thanks a lot


20 replies so far

View Wildwood's profile


2300 posts in 2101 days

#1 posted 11-24-2012 12:24 PM

Finish both sides of tabletop because of wood movement. Many people do not finish both side of steps & risers unless visible. Still have wood movement though. Same may hold true for outside steps, but would apply something on other side even if not visible.

Finish slows down moisture exchange in wood, but does not stop it. Why we finish wood, with oils, clear finishes, or paint depends on experience, end use, protection & preservation of wood we use.

-- Bill

View JesseTutt's profile


854 posts in 2077 days

#2 posted 11-24-2012 05:31 PM

You should always finish all sides of a project. You may not put as many coats or sand as much on the bottom of a table or on invisible parts of a stair, but it still needs to be finished.

I know professional carpenters that do not finish the bottom of stair treads or the vertical raisers. But, if I cared for the quality of the work or the person I was doing it for I would at least wipe on a coat of shellac or spray a coat or two of lacquer.

For a table I would apply the same number of coats and the same type of finish to all sides. Probably I would add an extra coat to end grain.

If I am not experienced with the finish or application method I normally start with an area that will not be seen and use that area as a learning event. Hopefully by the time I get to the really visible areas I have perfected the method.

-- Jesse, Saint Louis, Missouri

View MonteCristo's profile


2099 posts in 2155 days

#3 posted 11-26-2012 05:08 AM

I agree with the above comments but would add that the important thing is to seal these unseen surfaces with whatever sealant is the most efficacious, including cost wise. IE No point in spending a bundle on finish that will not be seen !

-- Dwight - "Free legal advice available - contact Dewey, Cheetam & Howe""

View gepatino's profile


217 posts in 2091 days

#4 posted 11-27-2012 04:20 PM

Thanks for the responses, I was thinking that all surfaces should be finished, but at the same time I’ve seen several pieces of furniture were the drawers seems to be unfinished, hence my doubt.


View darinS's profile


709 posts in 2834 days

#5 posted 11-27-2012 05:58 PM

I may be going against the grain here, but this gave me something to think about. Look at post #6, it’s by Hobomonk:

I know it got me thinking.

-- They say many people die because of alcohol. They never realized how many of them are born because of it.

View lumberjoe's profile


2899 posts in 2215 days

#6 posted 11-27-2012 06:01 PM

I would offer a contrary opinion. I never finish the underside of table tops. I know quite a few others here do not as well. You will read contrary information from anywhere you look. If you look at OLD furniture that is still around and doing well, you would be hard pressed to see a finished underside. Granted one can argue that they had nice, stable, old growth timber to work with. However we have nice climate controlled environments now (a/c in the summer, heat in the winter) that rarely see the wild temperature and humidity fluctuations these 100+ year old pieces were subjected to.


View Cosmicsniper's profile


2202 posts in 3125 days

#7 posted 11-27-2012 06:05 PM

I’ve mentioned this in a lot of threads recently. Finishes aren’t vapor barriers. Humidity is a vapor. It doesn’t matter what finish you use or what parts you finish. It will all move anyway. Finishes might somewhat delay the on-set of certain movement (that is debatable), but there is a reason why people don’t bother to finish the inside of guitars, drawers, table bottoms, etc. BTW, most of your big time finishing guys, like Flexner and Jewitt, including guitar maker Bob Taylor, believe the need to finish the entire project is a myth. I would concur.

-- jay,

View RussellAP's profile


3103 posts in 2253 days

#8 posted 11-27-2012 06:48 PM

Finish the bottom, but you don’t have to make it look nice with sanding too much, just smooth it out and apply the same finish so it’s sealed the same on both sides. I’d also pre finish it before you construct the table so your joints whatever they may be, are treated as well. I’m not talking about sealing tenons just the surface of where the tenon sits.

-- A positive attitude will take you much further than positive thinking ever will.

View lumberjoe's profile


2899 posts in 2215 days

#9 posted 11-27-2012 06:55 PM

The “sealed on both sides” is the myth Jay was talking about. Finish is an extremely poor vapor barrier. You aren’t going to spill anything on the underside of a table top, a dresser top, the back of the aprons, etc. The only thing you are trying to seal out is ambient moisture (vapor) – which finish does not really do.

Some schools of thought say that if you do not have some finish on each side, one side will take on or give off moisture more than the other. I feel (as well as many experts that Jay cited and personal experience) that if you start with good quality, DRY timber that you sand down to finish grits to close the grain as much as possible, you will be fine. Again, every piece of furniture that is 60+ years old and still around is proof of this. Adding a minuscule amount of finish which offers no vapor barrier only gives you piece of mind and more labor; no actual protection. There will be a lot of disagreement, but I am a scientific kind of guy. The science behind finish compositions supports this.


View gepatino's profile


217 posts in 2091 days

#10 posted 11-27-2012 07:08 PM

Well… this is getting very enlightening.

What happens when something is meant to be in the outside, like a deck, a pergola, a bridge… or even outdoors furniture. Does the finishing product servers to repel moisture, or as a protection for more agresive elements (sun, snow, ice, etc)?


View lumberjoe's profile


2899 posts in 2215 days

#11 posted 11-27-2012 07:12 PM

Nothing kills finishes quicker than mother nature :) Constant UV exposure, elements, drastic temperature shifts, etc will wear down the best of finishes quickly. Wood species selection is more important than finish selection here. You want wood that is naturally rot resistant (cedar, white oak, Ipe, locust etc) OR you want wood that has been pressure treated.

In addition, when is the last time you saw someone finishing or refinishing the underside of a deck?


View gepatino's profile


217 posts in 2091 days

#12 posted 11-27-2012 07:45 PM

lumberjoe: so the decking screws weren’t there to remove the boards and refinish? ;)

You are right, I’ve never seen anyone caring about the underside of a deck, but never saw how they make one… if they use some special finish in the underside…

But of course nothing (finish) will last forever. On the other side, I’ve seen a couple of wooden bridges here and there. Some of them could be more than 100 years old, they don’t look like if someone took much care on finishing them, but they are still there…

Unfortunatelly I don’t have time or space right now (I’m in the process of moving) to make some project and learn by doing, so I’ll keep asking questions once in a while.
Thanks for the patience (in advance)


View Cosmicsniper's profile


2202 posts in 3125 days

#13 posted 11-27-2012 08:14 PM

Most finishes are excellent moisture barriers…which means they can repel liquid. But they are still vapor permeable.

Outdoors, not much works against the elements, though for a while it does combat liquid moisture. But consider why latex is used outside our houses so much…it’s durable and flexible. It needs to be flexible because the humidity will cause expansion…and you don’t need the paint cracking because it is inflexible. Similarly, this is why spar varnish is used…because its a little more flexible than other film finishes (and it helps against UV).

Wood still moves regardless of the finish. You can’t stop that.

-- jay,

View Tennessee's profile


2861 posts in 2481 days

#14 posted 11-27-2012 08:55 PM

In my twelve years of running a refinishing shop, (1976-1988), I can’t even remember how many antiques of high quality came through my shop with unfinished inner sides.
Also, virtually every acoustic guitar made is unfinished on the inside.

I once read that the finest sealed finishes, such as epoxy based varnish, and wax sealers only stop about 53% of the ambient moisture. So if it takes the average table 48 hours to adjust to the humidity in a room, with a sealed finish will it take about 72 hours? Finishing undersides is simply a statement that some woodworkers want to make that they feel the job is not done properly, unless all sides are properly finished, and that is perfect for them, and their customers probably love it. But it makes no difference to the wood, and I finished baby grands worth thousands that had unfinished insides that I found before I started the refinishing process.

This is the same reason we all leave spaces in the panels on our kitchen cabinet panel doors, and so on. Because in reality, you can’t stop moisture.

-- Tsunami Guitars and Custom Woodworking, Cleveland, TN

View Clint Searl's profile

Clint Searl

1533 posts in 2328 days

#15 posted 11-27-2012 08:57 PM

Finishing the hidden parts is a waste of finish….unless it’s BLO, which is OK to waste is large quantities.

-- Clint Searl....Ya can no more do what ya don't know how than ya can git back from where ya ain't been

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