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Forum topic by zippymorocco posted 09-09-2016 06:37 PM 726 views 0 times favorited 15 replies Add to Favorites Watch
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zippymorocco

38 posts in 754 days


09-09-2016 06:37 PM

Topic tags/keywords: bar top table top fir reclaimed

Hello everyone,

I am designing a series of small tables for a bar. These are to replace some tables that someone else built and have since warped. I am thinking 28”X28” tops 1 1/4” thick. They will be reclaimed fir with various hardwood inlays and a QSWO edging. These tables will sit on a cast iron stand. I have a few questions that I am unsure of and would like others opinions if you all are willing.

1. with a 1 1/4”X24”X24” top will I need any additional cleats, plywood to insure they remain flat.
2. I will be using Enviro-Tex 2 part pour on finish for the tops (has to be this to match existing tops). Seems very impractical to use this part for the bottoms of the tables. Is there a recommended technique for finishing the underside to prevent warping

Thank you in advance for any information.


15 replies so far

View JBrow's profile

JBrow

819 posts in 386 days


#1 posted 09-14-2016 01:38 AM

zippymorocco,

I would think that plywood cleats would do little to counteract the forces that would cause the table tops to cup. If the top starts to cup, I suspect the forces acting on the top would easily overcome any resistance to cupping that might be offered by the plywood cleats. However, if the fastening system incorporated into the metal base prevents the wooded top from expanding or contracting, then incorporating plywood cleats that would be fastened to the metal base while allowing the top to expand and contract against the cleats would probably be a good idea.

I have not used Enviro-Tex 2 part pour on finish so I looked it up and can appreciate your reluctance in applying the finish on the underside of the table. However, by my way of thinking, the upper surface of the top will be fairly impervious to moisture. If the bottom surface of the top is not similarly coated, moisture could enter the underside of the top and cause underside surface fibers to swell which would encourage the top to cup (concave on the upper surface of the top). In the winter when the air is dry, more moisture could leave the underside of the top than from the upper surface causing the underside surface to shrink and encourage the upper surface to belly upward (convex on the upper surface).

As a result, in an effort to reduce the likelihood that the top will cup or belly, applying at least one thin layer of the Enviro-Tex 2 part pour on finish would be, in my view, good insurance. If for some reason, coating the underside of the tops with Enviro-Tex finish cannot be done then multiple layers of gloss polyurethane might work.

View jerryminer's profile

jerryminer

528 posts in 908 days


#2 posted 09-14-2016 01:52 AM

zippymorocco,

The lumber you use will matter—QS less likely to cup than flat sawn.

You make me nervous when you say “QSWO edging.” I hope you are not planning to introduce a cross-grain situation by wrapping an edgeband around the end grain of a solid wood top. If you don’t allow for wood movement, you can create problems.

Always safer to finish top and bottom the same.

28×28 x 1 1/4 should be OK if you use QS stock, use the same finish top and bottom, and allow for wood movement.

View Smitty_Cabinetshop's profile

Smitty_Cabinetshop

13738 posts in 2085 days


#3 posted 09-14-2016 01:53 AM

Finishing the underside will not prevent warping. Just plan on finishing the top. See PopWood article by Bob Flexner on wive’s tales regarding underside prep.

-- Don't anthropomorphize your handplanes. They hate it when you do that. -- OldTools Archive --

View zippymorocco's profile

zippymorocco

38 posts in 754 days


#4 posted 09-14-2016 02:12 AM

Thank you for the posts.

Jerry, when I say QSWO edging I mean a border. Probably a 1”-2” wide border of oak because it could take a little more abuse as compared to reclaimed fir. The Fir will be flat sawn only the edges will be quarter sawn.

JBrow, I think you might be on to something with the fastening system. The old tables were just screwed to the base with no allowance for movement. I will take this into account with the new tops.

My original thought was to coat the bottoms with a cheap poly to save time and money. However, now Smitty has me wondering if it is necessary at all. I always heard that you have to coat both sides equally until now.

Smitty, I sure like the idea of not finishing or at least not using the Enviro-tex to finish the bottom. Thank you for sharing the article. I will look into this further.

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jerryminer

528 posts in 908 days


#5 posted 09-14-2016 09:44 AM


Jerry, when I say QSWO edging I mean a border. Probably a 1”-2” wide border of oak because it could take a little more abuse as compared to reclaimed fir. The Fir will be flat sawn only the edges will be quarter sawn.

- zippymorocco

I’m still not sure, but hope you are not planning to create a “panel of doom” by introducing a cross-grain edge band. See this article.

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zippymorocco

38 posts in 754 days


#6 posted 09-14-2016 01:25 PM

Jerry,

Thank you for that information. Makes perfect sense. I was considering a breadboard for the ends rather than miters. Do you think that would work?

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JBrow

819 posts in 386 days


#7 posted 09-14-2016 01:39 PM

zippymorocco,

Leaving the underside of the table tops naked has the appeal of savings on labor and materials. However this short term gain can become a long term pain. When moisture can enter and exit the wood on one surface much easier than on another surface, the unbalanced movement of moisture greatly increases the changes of cupping or bellying of the top.

A simple test of this concept is to glue up a panel that is flat. Then leave the panel on the workbench for several days, so that moisture has difficultly transferring to the underside of the panel lying on the workbench surface. There is a real good chance the panel will cup in one direction or the other. Flip the panel over and after a few days the cup can reverse.

Some additional thoughts on whether to finish the underside of a table top, all recommending the application of finish to the underside of a table top, can be found at…

Keeping Table Tops Flat, a general discussion of a variety of tricks that can help keep table tops flat, including finishing tips…
https://www.finewoodworking.com/media/TabletopsFlat.pdf

How-To Apply Epoxy Finish, a step by step how to finish a tabletop with epoxy and lessons learned from cupped table tops…
http://logfurniturehowto.com/how-to-apply-epoxy-finish/

The DIY Guide to Finishing a Table Top, generally describes the steps for finishing a table top, including the underside…
http://www.familyhandyman.com/woodworking/staining-wood/the-diy-guide-to-finishing-a-table-top/view-all#step5

View Cooler's profile

Cooler

277 posts in 309 days


#8 posted 09-14-2016 02:52 PM

I made one replacement table top for a local Starbucks (and refinished the others). They were all about 24” x 24”, except the round one which was about 30” round. The tops were made from Baltic Birch plywood.

I made mine from regular hardwood ply which I wrapped with 3/4” x 1-1/2” stock. The veneer was maple as was the edging material. The edging was mitered and I used biscuits for added strength. I added a second thickness of material (solid stock, not plywood) under the center of the table top for a better thickness to screw the base onto. That piece was probably about 8” x 8” and was glued screwed.

I put four coats of oil based poly on all the tops and they looked remarkably like new when they were retired after 9 years of hard service. There may be other finishes that stand up as well, but this is the one I know will stand up from personal experience. And it is the fall back finish for hard wearing surfaces (and what I used on my kitchen counter top which was a purchased butcher block mateiral).

I think hardwood plywood is a far better option for the tables than solid materials. It may not suit your woodworking design ethos, but it will stand up better and will cost far less.

-- This post is a hand-crafted natural product. Slight variations in spelling and grammar should not be viewed as flaws or defects, but rather as an integral characteristic of the creative process.

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jerryminer

528 posts in 908 days


#9 posted 09-15-2016 03:51 AM



Jerry,

Thank you for that information. Makes perfect sense. I was considering a breadboard for the ends rather than miters. Do you think that would work?

- zippymorocco

Yes I do. They just take a bit of extra work.

View Rick M's profile (online now)

Rick M

7932 posts in 1846 days


#10 posted 09-15-2016 07:22 AM



Finishing the underside will not prevent warping. Just plan on finishing the top. See PopWood article by Bob Flexner on wive s tales regarding underside prep.

- Smitty_Cabinetshop

Flexner is wrong on this and I’ve debunked it before. If you read his explanation carefully it doesn’t even make sense. Ditto for Schwartz who has bought into Flexner’s mistake. Partly they base their conclusion on the examination of antiques but the problem is they are only examining the ones that survived and not all the ones that failed. What if 100 tables were built identically, 98 fail and 2 survive … if you only examine the survivors, you will draw a false conclusion and that is what happened. In Flexner’s case he also is contradicting his earlier work about wood movement and finishes, you can’t have it both ways … either a finish impedes moisture transfer or it doesn’t. There is no scenario where a finish impedes moisture transfer except specifically on the topside of tables. He lost his marbles with that theory.

Top and bottom should be finished equally and in turn .. top, bottom, top, bottom, etc. It’s all about airflow and moisture gain/loss. If you use quartersawn you significantly reduce the risk. Worst case scenario … I’m wrong but you follow my advice and the top doesn’t cup. Best case scenario … I’m right and you follow my advice and the top doesn’t cup. Note, there is no 100% guaranteed way to prevent a piece of wood from warping, it’s all about hedging your bets and doing the right things to equalize moisture transfer.

-- http://thewoodknack.blogspot.com/

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oldnovice

5731 posts in 2834 days


#11 posted 09-15-2016 03:55 PM

I agree with JBrow, not finishing the opposite side is asking for trouble down the road!
There is a reason that plywood always has an odd number of laĆ½ers!

-- "I never met a board I didn't like!"

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Smitty_Cabinetshop

13738 posts in 2085 days


#12 posted 09-15-2016 05:55 PM

I’ll never apply a beautiful finish to the underside of a table, or cabinet, or etc. Not debunked. Tens of thousands of pieces ‘survive’ from a time where it was so.

Got that much time? It’s a hobby, go for it. Trouble asked for, (it’ll never come).

-- Don't anthropomorphize your handplanes. They hate it when you do that. -- OldTools Archive --

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Cooler

277 posts in 309 days


#13 posted 09-15-2016 06:24 PM



I ll never apply a beautiful finish to the underside of a table, or cabinet, or etc. Not debunked. Tens of thousands of pieces survive from a time where it was so.

Got that much time? It s a hobby, go for it. Trouble asked for, (it ll never come).

- Smitty_Cabinetshop

I usually slap on a coat of shellac. I figure that any warping is due to moisture absorption, so any way I seal the underside from moisture is fine. Shellac dries fast and I usually apply a coat of shellac for my first coat of any clear finish. So it all fits my process.

-- This post is a hand-crafted natural product. Slight variations in spelling and grammar should not be viewed as flaws or defects, but rather as an integral characteristic of the creative process.

View Rick M's profile (online now)

Rick M

7932 posts in 1846 days


#14 posted 09-15-2016 08:25 PM

Yeah there is no reason for dried, milled, and finished wood to warp except through moisture exchange and Flexner has written previously that different finishes impede moisture at different rates. It was proven a million times over for hundreds of years before Flexner was born. Myth busting can be fun and no doubt gets website clicks but it’s possible to get carried away and start busting truths and that’s what happened here. I suspect antique tables with unfinished bottoms only survived because houses didn’t have conditioned air and the finish was shellac which isn’t a particularly good moisture barrier anyway. Set a table with an unfinished bottom near a register and see what happens … I can tell you from experience that in short order the top will cup. Same spot but a table with a finished bottom doesn’t cup.

-- http://thewoodknack.blogspot.com/

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Cooler

277 posts in 309 days


#15 posted 09-15-2016 08:28 PM

As a picture framer I can attest to the warping issue. A photograph (moisture impermeable) mounted on a mounting board will quickly warp, where as a paper poster on the same board will only warp slightly. The photo side does not absorb much moisture; the other side does.

But the poster does not affect moisture absorption very much so the warping is slight.

-- This post is a hand-crafted natural product. Slight variations in spelling and grammar should not be viewed as flaws or defects, but rather as an integral characteristic of the creative process.

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