Evan Book

Butcher Block Top Cupping

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Hey all, 

Relatively inexperienced DIYer, finished installing a large butcher block island top about a week ago. Noticed pretty immediately that it started bowing, cupping specifically. Hoping to get it laid back down but not sure what method is best.

It's a maple block, really two of them I cut and joined along the long axis with biscuits. The joint seems fine. I sealed the bottom before installation with oil based polyurethane, and after installation used a mineral oil/wax on top for the first few days. Wife decided she wanted to seal the top with poly after living with it a few days, about when the bowing was noticed. I stopped oiling it then in anticipation of lightly sanding the top and applying the poly to it. 

Anyway, I'm currently running a humidifier in the kitchen and using some weights to get it to lay down hopefully, and then after it does plan on sealing it completely with poly. Thoughts?

6641D817-758F-4D4B-876C-3230FF8AEF6B.jpeg

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31 minutes ago, Evan Book said:

It's a maple block, really two of them I cut and joined along the long axis with biscuits.

Welcome!

Two blocks that you made and the joined or were they purchased?

Is it cupping along the whole length or does it seem to hinge at the connection between the two halves?

Unfortunately, fighting movement after it happens is usually a losing battle. You may also be able to rip it down into some strips again, flatten, and the glue up again. 

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41 minutes ago, JohnG said:

Welcome!

Two blocks that you made and the joined or were they purchased?

Is it cupping along the whole length or does it seem to hinge at the connection between the two halves?

Unfortunately, fighting movement after it happens is usually a losing battle. You may also be able to rip it down into some strips again, flatten, and the glue up again.

Thanks for the reply,
 

I bought two blocks and joined them together. The bowing isn't really apparent at the joint, it's just the edges cupping up on each face grain side. Given that I bought the blocks and my experience level and limited tools, ripping it down is a bit daunting. Am I right in assuming that the cupping is caused by the wood on the top being dryer than the wood on the sealed bottom part?

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28 minutes ago, Evan Book said:

Thanks for the reply,
 

I bought two blocks and joined them together. The bowing isn't really apparent at the joint, it's just the edges cupping up on each face grain side. Given that I bought the blocks and my experience level and limited tools, ripping it down is a bit daunting. Am I right in assuming that the cupping is caused by the wood on the top being dryer than the wood on the sealed bottom part?

Depends, did it cup up? That says the bottom is wetter. 

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46 minutes ago, Tpt life said:

Depends, did it cup up? That says the bottom is wetter. 

It is cupping upward yes. So essentially the top dried out more than the bottom, which would make sense since I sealed the bottom but it was about 48 hrs or so between the bottom being sealed and the install being finished and oil being applied to the top. 

I guess the root question is, if the top reabsorbs some moisture will it eventually lay back down? And if so will it be able to reabsorb that moisture with the existing coating of mineral oil on top?

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17 minutes ago, Evan Book said:I guess the root question is, if the top reabsorbs some moisture will it eventually lay back down? And if so will it be able to reabsorb that moisture with the existing coating of mineral oil on top?

That is a big maybe. 

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2 hours ago, Evan Book said:

It is cupping upward yes. So essentially the top dried out more than the bottom, which would make sense since I sealed the bottom but it was about 48 hrs or so between the bottom being sealed and the install being finished and oil being applied to the top. 

I guess the root question is, if the top reabsorbs some moisture will it eventually lay back down? And if so will it be able to reabsorb that moisture with the existing coating of mineral oil on top?

I think that would need to be a pretty big humidity swing from where the top had been equalized to the space it was when you applied the finish. How long had you had the top before joining, and how long was your total process of joining the two sides together and then finishing?

Are you in an especially dry or humid area?

Keep in mind that all finishes still allow the wood to gain/lose moisture, they are not totally impermeable. 

Where did you buy the tops from? A large retailer or a local maker?
 

2 hours ago, Tpt life said:

That is a big maybe. 

Agreed. You might get lucky, but that’s what it would be- lucky. Unfortunately.

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Just looking at the image it looks like a long unsupported section hanging out between the legs and cabinet. Are there any battens under that part. It seems like that could be part of the problem. 

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Agree with @Barron, there seems to be a lack of support between legs and cabinet. 

My concern is the oil/wax applied to the top. That will virtually garantee that poky won't adhere, unless you sand or scrape to below the level of oil penetration.

The good news is that since you need to do that anyway, you can get serious about forcing some moisture in. My solutuon would be to sand the top aggressively, throw some damp towels on top, and iron the heck out of them to persuade steam into the surface. Check the flatness frequently. Adding corbels / battens of wood, or even steel angles (angle iron) underneath, running across the grain of the top, will help keep it flat. If you do that, be sure to make slotted screw holes in the batten so the top can expand and contract across the grain as humidity changes. Sand up to 180 or 220 grit and apply the poly, if all the oil / wax is gone.

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4 hours ago, JohnG said:

I think that would need to be a pretty big humidity swing from where the top had been equalized to the space it was when you applied the finish. How long had you had the top before joining, and how long was your total process of joining the two sides together and then finishing?

Are you in an especially dry or humid area?

Keep in mind that all finishes still allow the wood to gain/lose moisture, they are not totally impermeable. 

Where did you buy the tops from? A large retailer or a local maker?
 

Agreed. You might get lucky, but that’s what it would be- lucky. Unfortunately.

The tops came from a large retailer who gets them from a third party. I'm in central Ohio, so not an extremely dry or wet area. I do know the blocks shipped from Washington state, so a pretty big jump in environment right off the bat. 

 

I had the blocks for about 4 days before joining. Cutting was done on one day, and I sealed the bottom sides following that. Joining and install was done the next day.

 

Right now I'm using the humidifier and  hoping it lays down after several days.

 

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2 hours ago, wtnhighlander said:

Agree with @Barron, there seems to be a lack of support between legs and cabinet. 

My concern is the oil/wax applied to the top. That will virtually garantee that poky won't adhere, unless you sand or scrape to below the level of oil penetration.

The good news is that since you need to do that anyway, you can get serious about forcing some moisture in. My solutuon would be to sand the top aggressively, throw some damp towels on top, and iron the heck out of them to persuade steam into the surface. Check the flatness frequently. Adding corbels / battens of wood, or even steel angles (angle iron) underneath, running across the grain of the top, will help keep it flat. If you do that, be sure to make slotted screw holes in the batten so the top can expand and contract across the grain as humidity changes. Sand up to 180 or 220 grit and apply the poly, if all the oil / wax is gone.

That makes sense to me, I had originally assumed the steel legs would be enough support, given the thickness of the wood, but battens make sense, especially now.

Appreciate everyone's input!

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