Finishing both sides for expansion
#11
  
I have completed a walnut chest of drawers. Sides are wide boards, not frame and panel. The outside finish will be several coats of wiped-on Arm-r-Seal. My question is about finishing the inside so that moisture is equal?. Does the inside finish need to match the outside, or can I use some flooring polyurethane I have on hand.

Also, the drawer fronts will get finish on the inside, as well as the outside. But I hope to leave the drawer sides and back (1/2 inch walnut) uncoated raw wood. Will the sides expand at a different rate than the fronts? Will it matter? Joinery is half-blind dovetail.
Thanks, —Peter
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#12
  Re: Finishing both sides for expansion by petertay15 (I have completed a w...)
(02-19-2019, 05:01 PM)petertay15 Wrote: I have completed a walnut chest of drawers. Sides are wide boards, not frame and panel. The outside finish will be several coats of wiped-on Arm-r-Seal.  My question is about finishing the inside so that moisture is equal?. Does the inside finish need to match the outside, or can I use some flooring polyurethane I have on hand.  

I almost never put finish on anything inside a cabinet that can't be seen.  If I do, it's just a coat or two of shellac.  If you do put some finish inside don't use anything that's OB or it will stink for months/years.  Use shellac or WB products.   

Also, the drawer fronts will get finish on the inside, as well as the outside. But I hope to leave the drawer sides and back (1/2 inch walnut) uncoated raw wood. Will the sides expand at a different rate than the fronts?  Yes.  Will it matter?  No.  I've never had any joint failures anyway even with different wood species.  Joinery is half-blind dovetail.

Thanks, —Peter
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#13
  Re: Finishing both sides for expansion by petertay15 (I have completed a w...)
Just curious...is this your bowfront? or are you still working on that project. I don't recall seeing an end-of-project.


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#14
  Re: Finishing both sides for expansion by petertay15 (I have completed a w...)
To reiterate what John said: no oil based anything inside the chest. Personally I wouldn't worry about finishing the inside anyway.
I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.
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#15
  Re: Finishing both sides for expansion by petertay15 (I have completed a w...)
In reply, when making a tabletop, isn’t it IMPORTANT to finish the underside so that it won’t curve due to humidity? I’ve been taught that, so right or wrong?

Speaking of humidity, in Northern Illinois, RH is in the 90s in winter and also in summer. But in our house, in winter, the RH is 35%, so there is a wide range. (No central air or humidifier.). LAs I build this dresser, I consider the wood is already expanded, so I consider how it will shrink a bit.
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#16
  Re: Finishing both sides for expansion by petertay15 (I have completed a w...)
Not in my opinion. Here's what Flexnor has to say on the subject...I tend to follow his advice.
I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.
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#17
  Re: RE: Finishing both sides for expansion by petertay15 (In reply, when makin...)
(02-20-2019, 09:56 AM)petertay15 Wrote: In reply, when making a tabletop, isn’t it IMPORTANT to finish the underside so that it won’t curve due to humidity? I’ve been taught that, so right or wrong?

Speaking of humidity, in Northern Illinois, RH is in the 90s in winter and also in summer. But in our house, in winter, the RH is 35%, so there is a wide range. (No central air or humidifier.). LAs I build this dresser, I consider the wood is already expanded, so I consider how it will shrink a bit.

Table tops are flat and often poorly attached to the frame underneath, so I finish both sides.  You only have to lay an unfinished board on your bench for a day or two to see how it will cup one way or the other depending upon how much the RH changes to know that a thin board will follow the resultant difference in moisture from one side to the other.  Flexner has his opinion; I have mine.  


So why not the same treatment for a cabinet?  Because cabinet parts are reinforced by their construction.  Sides are held flat by the interior shelves and stretchers.  There's certainly no harm in finishing the insides but I haven't seen a genuine need.  If you look at those beautiful old pieces made by Goodard, Townsend, et al, nothing you couldn't see got finished.  They didn't get it right all the time; I've seen plenty of split sides and panels on those old pieces, but I can't recall ever seeing a piece by those guys where the cabinet side was warped.  Other pieces made by lesser mortals, yes, I've seen all manner of warp, split, etc.  

If the RH in your shop is 30% during the Winter and you are working on that piece it's going to EXPAND next Summer, not shrink.  If you are working in some unconditioned space, like an unheated shop (God love you if you are in Illinois in Winter) where the RH is 90% then, yes, it's going to shrink when you bring it indoors.  

John
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#18
  Re: Finishing both sides for expansion by petertay15 (I have completed a w...)
This forum is SO helpful! Thank you, John, for the complete explanation of how the solid cabinet construction mitigates the swelling problem.
(My outdoor shop is wood heated, fired up each morning, unless it’s zero outside. So the RH in the shop matches the outside, very high, summer and winter.)
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#19
  Re: RE: Finishing both sides for expansion by petertay15 (This forum is SO hel...)
(02-21-2019, 01:12 AM)petertay15 Wrote: This forum is SO helpful!  Thank you, John, for the complete explanation of how the solid cabinet construction mitigates the swelling problem.
(My outdoor shop is wood heated, fired up each morning, unless it’s zero outside. So the RH in the shop matches the outside, very high, summer and winter.)

So that explains why you said you would plan for it to shrink when you bring it inside.  All is well.  

John
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#20
  Re: Finishing both sides for expansion by petertay15 (I have completed a w...)
"Just curious...is this your bowfront? or are you still working on that project. I don't recall seeing an end-of-project."


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Sorry, I had you confused with Peter Tremblay and his bomba chest project.


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