Coffee table and wood shrinkage

[David Peterson]

This was my first attempt using rough cut lumber to build. I'd had some 5/4 cherry air-drying for about a year then brought inside for another 3 months or so. Without a moisture meter at hand I thought it should be good enough to go.

After construction I started to apply a finish to the table using Minwax Antique Oil finish. Within the hour after the first coat the table top started to contract along its width. I had thought it might try to bow at the edges or something but didn't expect to see it shrink. Doesn't wood expand with moisture? I went ahead and continued with multiple coats of oil, interested to see what happened. After three coats, allowing many days between applications, the 21" top shrank in width by as much as 1/4". The length was unaffected.

The pictures show the finishing in progress. Where the top was built to be flush with the frame the one pic shows that it was now set back by quite a bit. The bottom view shows the tabs that were used to secure the top - these tabs were captured in a slot along the inside of the frame to allow for seasonal movement. They were originally set with about 1/16" of clearance which has now opened up to 3/16". I'm wondering if I should reset those tabs closer to the frame; any more shrinkage and they will lose their hold. Or should I expect the table to expand again in the summer when there's more moisture in the air?

Wood never dies, does it?

247864247865247866247867247868

[Joe Angrisani]

.....After construction I started to apply a finish to the table using Minwax Antique Oil finish. Within the hour after the first coat the table top started to contract along its width. I had thought it might try to bow at the edges or something but didn't expect to see it shrink. Doesn't wood expand with moisture?.....

Just guessing, but I see what looks like a drop cloth of sorts under the table: Did you bring the table into the house from the shop for the finishing? My first thought is that the house, during the winter heating season, is dryer than the shop. I'll wager my two cents that the dry house interior has caused the final shrinkage.

We need to provide for seasonal movement, and we also have to assemble and build with consideration regarding where wood is in that seasonal cycle. If you size the top in the humid part of the year, it will shrink across the grain from there. If you size the top in the dry part of the year, it will expand across the grain when the humid months comes.

I wouldn't move the tabs. If you reinstall them to close the gap to 1/16" again, they'll be pushing out on the aprons by the time summer comes around.

[David Peterson]

Well, that makes sense Joe - that should have occurred to me. I built the table at my place in upstate NY, then brought it down to the office in NYC to finish. It's definitely drier downstate than in the Catskills. I just assumed that the finish was causing the movement and didn't think of the geography. It will be interesting to see what happens come summer.

[Mel Fulks]

Air dried wood will always move more than kiln dried .Kiln drying is a permanent change in the wood ,not just immediate water reduction. Even soaking kiln dried in water ,it will move much less than air dried . It's a nice pc.,just do what you can to asure that when in shrinking season it is free to move enuf to not crack.

[Joe Angrisani]

....at my place in upstate NY, then brought it down to the office in NYC to finish. It's definitely drier downstate than in the Catskills....

Just for the record, "Upstate" starts at Albany and the Mohawk River, not the Tappen Zee. The Catskills are solidly in Southern NY. ;) I'm an old Adirondack kid....

Will the table be free-standing, or will it live against a wall or other placement where you only see one long edge?

[Chris Fournier]

The design of your table does not suit solid wood. Simply because solid wood moves and your flush edge will not be maintained over 12 months of humidity changes. Don't worry, your table top will actually be too wide soon enough. The table top would have been better made from sheet goods that were veneered. Air dried or kiln dried makes no difference in how it behaves after it is down to the target MC. I have air dried tens of thousands of BFT of lumber and used tens of thousands of BFT of kiln dried lumber - do it right and both behave the same from a measurable stand point. Kiln dried is far too vague a term. There are many different types of kilns that use dry heat, moist heat, atmospheric pressure, vacuum etc. The finish has nothing to do with the dimensional change - it is an oil finish not H2O. The dimensional change has everything to do with the fact that you moved the table from one RH to another. A hygrometer is not expensive and is a woodworkers best friend, as is a moisture meter.

[Mel Fulks]

Next time we get specs that say the job must be done with kiln dried wood I'm going to quote you. I have two pieces of walnut here that were adjacent and air dried,part of a batch sent to us to be kiln dried. One piece went in the kiln and the other I withheld.Both have subsequently soaked in water the KD piece moves much less than the air dried. When both are allowed to dry the air dried piece moves inside the house ,the KD pc has no measurable movement inside the house. I posted about this before and invited all to see these samples,"pilgrims and doubters are welcome" Forest Products Laboratory is a good source for this type of information.

[David Peterson]

"Upstate" starts at Albany and the Mohawk River, not the Tappen Zee. The Catskills are solidly in Southern NY. ;)

Joe - for those of us in NYC, anything north of Yonkers is "upstate" :o

The table will be freestanding. It was built for a friend who just got a new apartment here. She is pleased as can be with it and wouldn't give a thought to any deficiencies in its build. As for the table top's set back, I think of it as a design feature and another lesson learned. The education continues - helped even more so with all the advice here.

[Joe Angrisani]

The table will be freestanding....

In that case I would center the top and attach it solidly in the center of the short ends. Make then other fasteners floating. Let the wood move on both sides of center through the year. This way the two long edges will always be uniform.



Joe - for those of us in NYC, anything north of Yonkers is "upstate" :o

At least you didn't say "The GWB".