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I have a cherry butcher block counter top approx. 5' wide x 8' long. I am having issues with it cupping in the 4' direction. My glue ups are lengthwise and the top has been coated top and bottom with tongue oil.
Does anyone have any suggestions or similar experiences?
 

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butcher block

The cherry butcher block is 2 3/4" thick and the glue ups are 1" thick on edge. The glue up was done 4 weeks ago in our shop. The material was around 6% MC @ the time of fabrication. The top was glued up and put in our clamp rack for one week, rotating it twice throughout the week. It then sat in our shop and was sanded and oiled for a one week period. We applied four coats during this time. The top was then delivered to the house and began cupping about one week later.
 

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It sounds to me like the relative humidity in the house is either too high or too low and is causing the top to cup. If you had no problem before it went and you do now i would think that the conditions inside the house are not what they need to be. Do you know if they heat with wood? Wood heat has a bad habit of drying wood out too much. It could be that the oil is drying off the top and remaing in the lower section thus swelling the wood and causing it to cup.

These are just ideas and hopefully they help you out.

Dave.
 

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Discussion Starter · #7 ·
Dave,
Thanks for the valuable information. The area of the top is exposed to sunlight via multiple skylights and windows. This may be causing the drying of the top and not the bottom. I do not know what type of setting the whole house humidification system is on, but I will check and make a recommendation. Do you know of any solutions, such as a different oil that may not evaporate as quickly that is compatible with tongue oil? Just a thought.
 

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Well you coated the top and bottom. Of course it is a humidity/MC issue.
Instead of assuming I am going to ask. Is the top convex or concave? I would assume it is convex. Almost always does it that way because the top tends to dry out more than the bottom because the cabinet doors prevent as much circulation as the top sees, meaning the RH humidity is lower on top, so the top is in compression overall.
I wonder what the MC was when it left your shop, and is it now in the house?
Are they living in the house now? Because if they are not, or even if they are for that matter remove a cab door or two and see if it flattens out in a week.
Is there any kind of appliance that could be causing the RH to be too high beneath the top.? Maybe a dishwasher right next to it and somehow there is stray steam geting into the enclosed area underneath during the drying cycle.
I know I'm reaching here.
They don't have the jacuzzi underneath there do they. ;)

It's puzzling I can't wait till you get it figured out.
 

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Sounds to me like what you need to do is take the top off if possible and turn it over and dry it out and see if it flattens out. If and when it does do not apply any more oil to the bottom and only have the customers oil the top periodically. It may cup a little but my bet is that the sun will evaporate it quickly enough that it should never do it again.
 

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You have to get those UV rays before they get the countertop, however you have to do it. I don't know if a UV sealer would stop the heat right there at the top or not I doubt it.
Maybe Dave can figure it out some more I am stumped.
 

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Another common(lately) problem revolves around installations. There are cabinet bases that have dust covers. If the top...any solid wiood top is placed directly onto this capped cabinet the bottom is essentially sealed by the surface below. This of course creates the imbalance top to botoom.

Also seasonally we see some movement. If there is something causing the environment below the top to be different or maybe slower reacting than the environment above it then warp is to be expected. This sometimes can be caused by things like wood burning stoves or HVAC with out humidification.

One things is clear if the top is cupping up or "smiling" as we like to say either the top is losing moisture or the bottom gaining...or both.
 

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If i had to make a guess, i would bet that the oil is the culprit,its drying on the top because of exposure to air movement, at a much faster rate that the bottom, have run into this before, always be sure you use good drying oils, and simply put the pure ones aint it,if you remove the top flip it over and reverse the situation, you will probably see it reverse itsself to flat, many years ago when i had to do refinishing to eat, we used to get a ton of table leaves that were cupped and we would simply wet the concave side and then put it in the sun with the convex side up and if you wasnt careful it would reverse,cupping in many cases is simply caused due to moisture imbalance from one side to the other, and i really think this is the problem here....best of luck
 

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Screw a few pieces of angle iron, cut to fit inside the cabinet, to the underside of the countertop . This is how Bowling lanes are made up.
 

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OFF TOPIC:

BTW what are bowling lanes made of [what kind of wood?] and what kind of finish?

Seems to me both the bowling lanes and skating rinks have the same kind of wood and finish - is that right?
 

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The top dried out more than the bottom.
Why? Oil allows the moisture to go out quick. The bottom side is inside the cabinets and gets enough of a different moisture exposure than the top (yes inside a closed cab).

Solution. Removed and both sides exposed, it "may" flatten.
If it doesnt flatten, and the bend is very localized (down 1 piece or a narrow width area) you may be able to rip/reglue it.
jim
 
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