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Bowed cutting board - FS7 - 07-29-2019
I have two young children so my shop time is limited, and what I do get can be abruptly terminated with no real idea of when I'll get back.
I have an end grain cutting board that was finished mostly on one side when life happened and it sat with a heavy coat or two of mineral oil on one side. When I finally got back to it, it had bowed. Is it as simple as finishing the other side, turning it over, and waiting for the moisture to equalize?
I am curious because I imagine the mineral oil on one side will retard moisture transfer and it will be limited to the other side (now the concave side) for the most part. I supposed I could oil that side heavily and then when moisture exchange is even through both sides it will eventually fix itself. It was perfectly flat prior to oiling. Also, it's been on painter's pyramids, so it did have airflow on both sides.
RE: Bowed cutting board - Stwood_ - 07-29-2019
I'd give the oiling the second side a try before having to cut and flip the pieces.
RE: Bowed cutting board - hbmcc - 07-29-2019
Your evaporation differential is too much as it is with only one side oiled. That, or the side that's swollen was directly on a surface and wouldn't equalize. Slop oil on the unfinished side, and then; put little feet on the bottom--maybe, rubberized--so it won't slide off the counter and will weather equally.
RE: Bowed cutting board - FS7 - 07-29-2019
(07-29-2019, 11:31 AM)Stwood_ Wrote: I'd give the oiling the second side a try before having to cut and flip the pieces.
This is what I'm trying now. It's a checkerboard pattern with a center strip (also end grain) so cutting and regluing isn't really practical.
RE: Bowed cutting board - BaileyNo5 - 07-29-2019
This might be worth a look.
Correcting Warps
RE: Bowed cutting board - mr_skittle - 07-29-2019
Sorry I don't have any ideas on how to deal with your cutting board, but as a fellow parent of 2 young kids, I totally identify with your shop time issue. My older one is 7 now and its been just about that long since I had shop time before 8pm. Children have a way of consuming your time but just wait. I figure it's just another decade or so and we can get back to some uninterrupted shop time. Hang in there!
RE: Bowed cutting board - MichaelMouse - 07-30-2019
(07-29-2019, 07:39 PM)BaileyNo5 Wrote: This might be worth a look.
Correcting Warps
Couple things come to mind. First, oil and water don't mix, and oil is not ADsorbed by the cellulose, thus making it fatter. It is ABsorbed, and fills the available space where water would like to exit. So what you had was maybe a change in RH over time which allowed moisture to escape the side which was not blocked up with oil. Or you started too wet and blocked the loss from the one face, but not the other. Flexner's idea of adding moisture to the compressed side to relieve the set may be all you need, other than time, though his idea of squeezing the oiled face sounds as if it might help.
In any case, lesson learned, I'm sure, to finish (or treat, as mineral oil is NOT a finish) both sides of an endgrain board. Should stay pretty flat even if you start with wood above the EMC.
RE: Bowed cutting board - FS7 - 08-13-2019
I've tried a few things now. Simply oiling and letting it sit had no appreciable effect.
I tried to wet the concave side (with morning dew) and set it in the grass until the sun baked it a bit. This caused deformation in the short direction (the bow was in the long direction). This is odd to me, since it's obvious moisture exchange is taking place.
I have since kept it clamped in both directions, using the tendency of the clamped piece to bow away from the pipe (or bar). After a few days, it seems to be evening out somewhat. With a straightedge, it looks the concave face in each direction (opposing directions) is around 1/16" low in the center. If it keeps improving it will certainly be acceptable.
Years ago I had a rubberwood cutting board I got from a box store and I remember it warped badly at some point because it got wet underneath and I wasn't aware. I bought another and let that one sit in the shop, and after a long time (I couldn't tell you how long, maybe a year) it had equalized to the point that the warping was gone. Knowing that no finish is truly waterproof, with this once being flat I am pretty sure it will eventually even out.
RE: Bowed cutting board - Kansas City Fireslayer - 08-15-2019
Time for the drum sander or low angle bench plane. Reflatten and refinish both sides. Make sure you wipe up fluids right after using. That’s what dips mine more than anything. Wife and kids aren’t as attentive so off to DS a couple times every year. I like to keep mine looking very fresh though. I agree with rubber feet. HD has nice soft rubber ones cheap. SS screws don’t rust. Put a 1” diameter 1/8” deep hole for the feet to rest in so it’s not so jacked up in the air.
RE: Bowed cutting board - BigD - 08-22-2019
(07-29-2019, 10:13 AM)FS7 Wrote: I have two young children so my shop time is limited, and what I do get can be abruptly terminated with no real idea of when I'll get back.
I have an end grain cutting board that was finished mostly on one side when life happened and it sat with a heavy coat or two of mineral oil on one side. When I finally got back to it, it had bowed. Is it as simple as finishing the other side, turning it over, and waiting for the moisture to equalize?
I am curious because I imagine the mineral oil on one side will retard moisture transfer and it will be limited to the other side (now the concave side) for the most part. I supposed I could oil that side heavily and then when moisture exchange is even through both sides it will eventually fix itself. It was perfectly flat prior to oiling. Also, it's been on painter's pyramids, so it did have airflow on both sides.
One way to keep one face from soaking in more mineral oil than the other is to place the entire board into a pan that is deep enough to hold the board and oil above and below the board. When you do this, the board will float in the oil, so you need to provide some way to hold down on the top of the board to keep it submerged. Since your board has one face that has soaked in more oil than the other, I would try this method. Let it soak for a couple of days held down so it is completely submerged. The oil should even out on both surfaces which should flatten it out.