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Balance between top and underside

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Forum topic by illusioneer posted 02-22-2016 01:32 PM 453 views 0 times favorited 7 replies Add to Favorites Watch
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illusioneer

10 posts in 287 days


02-22-2016 01:32 PM

Topic tags/keywords: countertop cherry balance question finishing

I am making two 12’ cherry countertops. I know treating the top side and underside the same is needed to keep moisture balance and prevent warping. My question is; If I am using a varnish to finish the top side, can I use polyurethane on the underside and have it maintain balance, or must the type of finish match on top and underside? (So it won’t warp or bow)

-- We all have a moral obligation to make the world a better place, through integrity and disposition. " be joyful, and the world becomes a better place!"


7 replies so far

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OSU55

1056 posts in 1449 days


#1 posted 02-22-2016 02:34 PM

Poly on bottom will be fine. The surface just needs to be sealed as well as the opposite side. The film thickness does not have to be the same. 2 coats of thinned poly, 20% or so, will do it.

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illusioneer

10 posts in 287 days


#2 posted 02-22-2016 02:56 PM

Thank you. That’s what I thought just wanted confirmation.

-- We all have a moral obligation to make the world a better place, through integrity and disposition. " be joyful, and the world becomes a better place!"

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illusioneer

10 posts in 287 days


#3 posted 02-23-2016 06:06 PM

Quick follow-up question, will de-waxed shellac work too?

-- We all have a moral obligation to make the world a better place, through integrity and disposition. " be joyful, and the world becomes a better place!"

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upinflames

209 posts in 1622 days


#4 posted 02-23-2016 08:06 PM

De-waxed will work…I don’t bother with both sides unless it’s in view.

Look at some of the fine works from many moons ago, no finish on a lot of unseen surface.

The humidity does cause wood movement, just not nearly as much as folks exaggerate. Years ago the houses were not as “tight” as they are now and the furniture survived just fine.

I’ll have to get some pics of a china cabinet that is 120years old, no finish on the underside of the top or bottom. BUT I am sure the internet wizards will be here shortly to let you know how they would do it.

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OSU55

1056 posts in 1449 days


#5 posted 02-24-2016 12:56 PM

Waxed or dewaxed shellac will work to seal the underside as well as any other unseen surfaces. I use both, but usually dewaxed because I use it as a toner (with Transtints) under the topcoat. Don’t use waxed under another finish. I seal all unglued surfaces.

While I’m not an internet wizard, it’s best to seal all surfaces. Especially today with most homes fairly well environmentally controlled, wood movement is less of an issue, but if the project gets put in storage or something, it could come out a bit potato chipped. Some joints may only move .020-.030”, but it becomes noticeable depending on where it is. I also have antique furniture, and the effect of wood movement is very noticeable.

Wood movement is real, whether exaggerated or not. It depends on several factors. You spend a lot of time and $ to build something, and sealing the surfaces is pretty cheap and not much time in the overall scope. I see it as cheap insurance. But hey, if you want to argue that world is flat be my guest…........

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illusioneer

10 posts in 287 days


#6 posted 02-24-2016 10:26 PM

Thanks osu55, I will be taking the precautions… Too much money and effort to risk.

-- We all have a moral obligation to make the world a better place, through integrity and disposition. " be joyful, and the world becomes a better place!"

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shampeon

1711 posts in 1643 days


#7 posted 02-24-2016 10:46 PM

I love shellac, it’s a great sealer, and an easy finish. But I wouldn’t use it as a top coat on countertops. It’s fine if you want to seal the thing top and bottom with shellac, and then top it with poly. As someone is bound to point out, though, you could also just seal with thinned poly and not have to switch mediums.

-- ian | "You can't stop what's coming. It ain't all waiting on you. That's vanity."

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