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You said it Joe…. he is a writer and teacher. For those of us that has years in the field working with wood, we understand what works and doesn’t.
Paul is right, however I can only assume your writer was probably talking about MDF….
Joe,
Being a writer and teacher does not make him right. Experience in making real products to use in real environments most likely goes much further to enhance a persons knowledge base. I have built hundreds of table tops over the years and you definitely have to finish both sides if you don’t want to be hanged by your clients.
We would pass several tops thru the thickness sander late on a friday and set them aside for finishing the following week. They would be stacked one on top of the other, with only the top one exposed on one side. Two days later the top on the top of the pile would be warped badly from differential moisture uptake. As much as 1″ or more bow. The top exposed surface expands with the extra moisture and the protected bottom does not. Voila, major bow.
An applied finish on wood slows moisture uptake on the applied side. The other side has no barrier, so it takes up moisture faster. BOW! The other misconception is that application of a heavy build finish stops moisture migration. Wrong!! It only slows it down. Both surfaces have to be trated equally if a top is to have a fair chance of staying flat.
Paul
KC and Paul:
Please don’t confuse the opinion I posted with that of mine. I didn’t say I disagreed with Paul, I said the author did and gave his credentials. Readers have to weigh for themselves.
Joe
Hi Joe,
We got a job to engrave the logo of a Canadian brewing company ( a Stag Head, as in looks like a deer) into the tops of bar tables the other day. The tables are pine and have been in use in two bars for several years. The tops were coated with a heavy bar top plastic finish. The bottoms have no finish.
The tops arrived at the shop today and guess what? Up to a 1/2″ warp across a 30″ wide top. It’s up on the edges and down in the middle as would be expected with differential moisture uptake on the bottoms. The bottom expands more than the top does creating the warp. We need to flatten the tables before CNC cutting begins. The top finish has been removed and we will mist water onto the tops over a few days to expand the top surfaces and flatten them before continuing. After cutting the tops will be finished equally on both sides.
Just a typical day to day example in the real world of woodworking versus the academic world of teaching.
Paul
Posted By Paul Bingham on 19 May 2010 05:29 PM
Hi Joe,We got a job to engrave the logo of a Canadian brewing company ( a Stag Head, as in looks like a deer) into the tops of bar tables the other day. The tables are pine and have been in use in two bars for several years. The tops were coated with a heavy bar top plastic finish. The bottoms have no finish.
The tops arrived at the shop today and guess what? Up to a 1/2″ warp across a 30″ wide top. It’s up on the edges and down in the middle as would be expected with differential moisture uptake on the bottoms. The bottom expands more than the top does creating the warp. We need to flatten the tables before CNC cutting begins. The top finish has been removed and we will mist water onto the tops over a few days to expand the top surfaces and flatten them before continuing. After cutting the tops will be finished equally on both sides.
Just a typical day to day example in the real world of woodworking versus the academic world of teaching.
Paul
Paul:
Again, I must remind you that I have never made a claim either way. I read an article that disagreed with your position and posted it. Readers can pay the $1.98 and judge for themselves. Dissent is the beauty and value of this forum.
Thanks,
Joe
P.S.:
Speaking of academics vs. real world, I had a friend who was taking an art class. I told her if she sanded and flamed the edges of her Plexiglas project, they would turn clear. When she did and her classmates were amazed, her professor announced that flaming edges of Plexiglas “would never work”.
Posted By Paul Bingham on 19 May 2010 05:29 PM
Hi Joe,We got a job to engrave the logo of a Canadian brewing company ( a Stag Head, as in looks like a deer) into the tops of bar tables the other day. The tables are pine and have been in use in two bars for several years. The tops were coated with a heavy bar top plastic finish. The bottoms have no finish.
The tops arrived at the shop today and guess what? Up to a 1/2″ warp across a 30″ wide top. It’s up on the edges and down in the middle as would be expected with differential moisture uptake on the bottoms. The bottom expands more than the top does creating the warp. We need to flatten the tables before CNC cutting begins. The top finish has been removed and we will mist water onto the tops over a few days to expand the top surfaces and flatten them before continuing. After cutting the tops will be finished equally on both sides.
Just a typical day to day example in the real world of woodworking versus the academic world of teaching.
Paul
Paul, We’ve done the same thing by misting water on the wood with the concave side up and placing quartz lights under the tops towards the convex side the heat will help speed things up and flatten within a day.
Steve
Just checked on the tops this morning. 24 hrs after two misting sessions and the tops are mostly flat and ready for the CNC.
Paul
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