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Cutting Boards should be called Cupping Boards

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Forum topic by GerardW posted 10-26-2014 08:35 PM 1497 views 0 times favorited 9 replies Add to Favorites Watch
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GerardW

44 posts in 1290 days


10-26-2014 08:35 PM

ok. So my foray into making end grain cutting boards for family this christmas has become a study in board cupping. First came the realization that a board can go through my planer cupped and still come out cupped. And I’m okay with that (well I’m okay with the physics of it at least). So I built a router planing jig to both register one side and to plane my finished end grain surfaces. It worked very well.

Now I’ve come back to some of the planed end grain boards (I’ve been amassing them to finish them all at once) to find them cupped. Severely. When they were not before. Needless to say, this is maddening. I can shave more off with my router planing jig, but at some point if the cupping doesn’t stop I will be left with some very expensive end grain veneers.

Why is this happening? And more importantly, how do I stop it?

-- Gerard in Bowie MD


9 replies so far

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firefighterontheside

13523 posts in 1324 days


#1 posted 10-26-2014 08:54 PM

Keep them in a controlled environment and seal them with mineral oil or a mix of mineral oil and beeswax. If you have to keep them outside, sticker them as you would drying lumber so that the air circulates around them and they don’t dry more or less on one side than the other.

-- Bill M. "People change, walnut doesn't" by Gene.

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Yonak

979 posts in 988 days


#2 posted 10-26-2014 09:02 PM

You could cut a dado in the middle of the edges before they cup and insert strips of wood. You could sand the strips flush with the edges of the boards or you could have them stick out a little bit, with rounded edges for an additional design feature. You wouldn’t want them to stick out too far as they would get in the way when scraping cut food off the edges of the boards. Keep in mind it wouldn’t be good to get too fancy with the meeting up of the ends of the strips (such as mitres and the like) as their relative positions will vary slightly with changes in environmental conditions.

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Ger21

1047 posts in 2598 days


#3 posted 10-26-2014 11:00 PM

Store them standing on edge, and they should stay flatter. Moisture needs to enter and exit froim both the top and bottom at the same time, or they’ll cup.

-- Gerry, http://www.thecncwoodworker.com/index.html http://www.jointcam.com

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jerryminer

528 posts in 909 days


#4 posted 10-26-2014 11:21 PM

1. Did you let the wood acclimate to shop conditions before milling? (if not, they are going through a moisture change)

2. How are you storing them after milling? They need to have both faces open to the air in order to remain flat. If you stack them, or set them on a table or bench without stickering, they will gain/lose moisture unevenly—and cup

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Dallas

3599 posts in 1955 days


#5 posted 10-26-2014 11:29 PM

More pictures of the top and bottom would help.
At first thought I would say the pieces weren’t alternated as to direction when laying the board out.

I’m not sure that the acclimation was a problem although it very well could have been.

-- Improvise.... Adapt...... Overcome!

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waho6o9

7179 posts in 2044 days


#6 posted 10-26-2014 11:45 PM

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GerardW

44 posts in 1290 days


#7 posted 10-26-2014 11:55 PM

Thank you to everyone for the replies. In light of what has been shared, I think that improper storage in my garage (with varying humidity) is the culprit here. I had the “finished” boards stacked on top of one another- and no surprise that the board on top is cupped the worst. I’ve moved them inside where the temp and humidity are more reliable, I’m storing the ones that aren’t that bad on their ends, and the worst I have clamped against the cup (Per http://www.thewoodwhisperer.com/articles/cutting-board-warping/)

I also want to take a moment to say how amazing it is to be a jock here. I was feeling really down on the boards inexplicable cupping, and the quick response from the LJ community let me know that I am not the only one and not just (totally) inept.

-- Gerard in Bowie MD

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firefighterontheside

13523 posts in 1324 days


#8 posted 10-27-2014 12:17 AM

I’ve “fixed” cupped boards before by wetting the concave side and the. Allowing to dry evenly on both sides. Cupping happens when one side dries(shrinks) and the other side either stays the same or even gets wetter and expands. I realized that I had caused the problem by leaving a wide board laying flat on the bench for a day.

-- Bill M. "People change, walnut doesn't" by Gene.

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bannerpond1

397 posts in 1366 days


#9 posted 11-03-2014 11:57 AM

I have had this happen because I did not stand the boards on edge to allow them to acclimate. As soon as I turned them on edge, the bow went away when the other side dried.

Off the wall question: Are you sure your saw blade was a dead 90 degrees? How about the fence on your jointer? Anything off will be multiplied.

Did you maybe induce the bowing by failing to put cauls across the face when you clamped the pieces? I use a dead flat table to glue up the boards and make sure I’m not tightening the clamps so tight that I induce a cup. The placement of the clamps on the edge of the board can cup the whole thing if the clamps are not centered on the thickness.

I think it’s a matter of drying the boards with both faces (end grain now) exposed.

-- --Dale Page

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