Why do all my wooden cutting boards have cracks in them?
January 2, 2017 9:03 PM   Subscribe

I have a bunch of wooden cutting boards, and they all have some form of split on one side, usually on the glue seam. Why does this keep happening, how can I fix my boards, and how can I stop this from happening?

This is the split end of one of the boards. The split goes through the depth of the board, but not more than a few inches on one side. When I first got that board, I treated that board with JK Adams Mineral Oil a number of times over a week or two, and it seemed healthy and fine. The other two boards are like that with varying degrees of issues. None of my boards are end-grain boards, for what it's worth.

The main thing I can't figure out is how to repair them. Titebond III seems to be a good wood glue that's food safe, but how do I apply it? Do I fill in the cracks and then clamp the board, or would that cause stress elsewhere and may cause it to crack? Is there something else I can do, or should I start over and get some new boards? (In case it's not obvious, I'm not particularly well-versed in wood repair...)
posted by gchucky to Home & Garden (33 answers total) 6 users marked this as a favorite
Do you wash them in the dishwasher? It might be the water then heat that is warping them
posted by calgirl at 9:06 PM on January 2, 2017 [6 favorites]

How much did you spend on that board?

Have you ever oiled it? Good cutting boards cost a bit and will last decades with regular oiling.

That level of cracking will diminish, but proabably not disappear, with a few weeks of frequent application of mineral oil.

Don't soak it in water ever, only use soap when you have to.
posted by SaltySalticid at 9:07 PM on January 2, 2017 [2 favorites]

How are you cleaning them? (I'm wondering if they're splitting from going through a dishwasher.)
posted by lazuli at 9:08 PM on January 2, 2017

(Sorry I failed to notice your oiling regimen, given that, water and too extreme of wet/dry cycles are almost surely to blame.)
posted by SaltySalticid at 9:16 PM on January 2, 2017

Every wooden chopping board made from multiple pieces will eventually come to bits. I have never even once seen such a board last more than five years.

It keeps happening because you simply can't oil such a board deeply enough to prevent washing water seeping in through the cutting scratches, and even if you could, the oil itself would swell and warp the board enough to crack the glue seams.

I have a fifteen year old 340x290x19mm chopping board cut from a single piece of pine. It's had many trips through the dishwasher, it's been left outside in the sun, it's been soaked in hot water and detergent, it's been treated with linseed oil maybe twice, it's cut and scratched and scored all to hell, and it's giving me no reason to expect it not to last another fifteen years. Get one of those.
posted by flabdablet at 9:40 PM on January 2, 2017 [4 favorites]

Response by poster: The boards have never gone through the dishwasher, no.

When I do clean them, I put them in the sink, scrub them with a natural dish detergent (from Costco) and water, and then dry them with paper towels, and then angle them against a wall to finish drying. After I've carved up a chicken or a turkey and there are liquids and juices all over the place, just drying them off with paper towels seems unsanitary.

And given the cracks that are there now, what's the best way to repair them?
posted by gchucky at 9:41 PM on January 2, 2017

Best answer: Titebond III seems to be a good wood glue that's food safe, but how do I apply it? Do I fill in the cracks and then clamp the board, or would that cause stress elsewhere and may cause it to crack?

If you're so attached to these boards that you really don't want to replace them and you really do want to repair them in a way that gives them any chance at all of lasting more than a year before they crack again, what you'll do is as follows:

1. Bake the board in a low (70-90°C) oven for a couple of hours to get it as dry as dry as dry.

2. Rip along the existing glue seam with a bench saw, then plane the cut surfaces, then fix the pieces together again with dowels and glue and clamps.

3. After the glue has set, remove the clamps and sand the board along the new seam until no visible trace of glue overspill remains.

4. Oil the bejeezus out of the board with raw linseed oil (don't use boiled oil as it contains non-food-safe hardening agents), replace the clamps, and bake the board again to make the oil penetrate and harden.

5. Repeat step 4.

6. Lightly sand all over with fine sandpaper to get rid of the fuzz of oil-encrusted wood fibres.

7. Rub over with a little more linseed oil, then wipe off as much as you possibly can with a clean rag.

8. Leave the board unused for a week or so to let the oil harden completely.

Then you'll never never never immerse the board in water again. Instead, what you'll do when it wants cleaning is a preliminary scrub with dishwashing detergent alone and a brush, then rinse that off under running cold water, then dry the board with a tea towel and apply a bit more linseed oil (which will do its best to displace any water stuck in cracks and cuts).

Or you could just get a one-piece board instead and subject it to years of merciless abuse. Your call.
posted by flabdablet at 9:58 PM on January 2, 2017 [13 favorites]

Best answer: Mineral oil, by the way, is not a wonderful wood preservative. It penetrates well and displaces water well, but it doesn't ever harden. That means it will just keep on penetrating the wood, eventually causing it to swell.

Linseed oil is better because it penetrates far enough into the surface to get below the likely depth of knife scores, then polymerizes and hardens into a tough and flexible almost-plastic.
posted by flabdablet at 10:04 PM on January 2, 2017 [12 favorites]

Best answer: Also, if you lean a board against a wall to finish drying, you're creating a damp zone along the bottom that takes far longer to finish drying out than any other part of the board. That's pretty much the best way to maximize swelling-induced stresses on the ends of a glue joint. Your board will be far better off if you air-dry it in a dishrack instead.
posted by flabdablet at 10:07 PM on January 2, 2017 [8 favorites]

With what chopping boards go through in terms of daily wear and tear I don't think the cracks you are seeing are really avoidable in a glued board.

I've made a lot of chopping boards for people and I would never consider gluing a board. Use a single piece of timber, split, knot and void free. If you are buying rather than making one then look for the same. Stay away from boards with filled knot holes and the like.
posted by deadwax at 10:16 PM on January 2, 2017 [1 favorite]

Another thing that hasn't been mentioned; you shouldn't use wooden cutting boards for animal meat, and especially not uncooked animal meat, as it's basically impossible to completely clean and disinfect a wooden board in a way that won't damage it. Use a plastic board that can go through the dishwasher for meats. Reserve your wooden board for fruits and veggies.
posted by Aleyn at 10:26 PM on January 2, 2017 [6 favorites]

Incidentally, linseed oil is the same thing as flaxseed oil*, so if you want to be sure you're getting something food-safe, you can get some sold as a dietary supplement and use that. As sated above, linseed oil is a "drying" oil which means it polymerizes on its own. This is exothermic, meaning it releases heat, so don't wad up a whole bunch of flaxseed-soaked rags together, because they'll spontaneously combust. If it's mixed in with enough other stuff, it'll be fine, so this is more of a "fun fact" than an actual safety tip; unless you're also treating a bunch of furniture or wainscoting or something at the same time, you're not going to make enough flax-soaked waste for it to be an issue.

* also, linen and linoleum are made from flax
posted by aubilenon at 10:39 PM on January 2, 2017 [4 favorites]

2nd on getting a plastic board for meats. Definitely more sanitary. When I did that and started keeping the wood board for veg I saw the life of my boards automatically increase.
posted by MandaSayGrr at 10:39 PM on January 2, 2017 [1 favorite]

flabdablet provided a great answer. The board that you took the photo of split on the end first -- meaning it absorbed water through the side. That makes sense because end grain is WAY more porous. You have to oil the edges of the board much, much more heavily than the cutting surface. You also want to avoid letting the board lean on its edge in standing water.

The wood whisperer makes a good case for sealing cutting boards with a 50/50 blend of varnish and oil and I know a lot of guys use that with good results, although I've never tried it.

Using just Titebond will fail probably after about 6 months and epoxies aren't (as far as I've ever seen) actually food safe.
posted by Lame_username at 10:52 PM on January 2, 2017

Best answer: you shouldn't use wooden cutting boards for animal meat, and especially not uncooked animal meat, as it's basically impossible to completely clean and disinfect a wooden board in a way that won't damage it.

That's common advice, but unsound. Wood kills microbes as it dries. As long as you scrub your wooden board clean and let it dry completely before using it again, it will look after you better than your plastic board will.
posted by flabdablet at 10:54 PM on January 2, 2017 [24 favorites]

Yeah there's no reason not to use a wooden board for animal proteins so don't worry about that.
posted by Carillon at 11:21 PM on January 2, 2017 [1 favorite]

Mod note: Please drop the meat discussion at this point, and focus on the actual question. Thanks.
posted by taz (staff) at 11:37 PM on January 2, 2017 [1 favorite]

This is (unfortunately) how wood behaves. The end grain gets wet and when it dries the ends dry out quicker and more thoroughly than whatever wood comes "further inside" the plank. Inner tensions ensue. As most glue isn't truly permanently waterproof, this is the typical failure you'll see in assembled boards because the glue line is the weakest area.
If possible, one should use planks from quarter-sawn wood in one piece. That's how the better planks are made.

You can solve your problem by ignoring it as long as possible. When the glue line finally fails, you need to re-shape the gluing surfaces using a sharp hand plane. Flip the board sides back to back, so the to-be-glued surfaces are more or less lined up. Secure both plank sides so nothing shifts while planing. Plane the glue surfaces straight and smooth, then flip the plank back flat and glue together using clamps, some extra wood bits to avoid clamp marks, and waterproof titebond glue. Make sure to clamp the plank flat on your work surface, too, to avoid it from buckling under the sideways pressure.
If you're equipped with the right tools and workspace, this takes 20 minutes. Let the glue dry overnight before un-clamping.
posted by Namlit at 12:49 AM on January 3, 2017 [2 favorites]

When I do clean them, I put them in the sink, scrub them with a natural dish detergent (from Costco) and water, and then dry them with paper towels, and then angle them against a wall to finish drying.

This sounds like a pretty good routine, provided you keep the time that they're in the sink sitting in water to a minimum. They should NEVER be allowed to soak in water, even for a few minutes. What you're seeing here is a compression failure. Water soaks into the end grain much faster than through other surfaces, so the cell walls near the end of the board begin to swell, just as a dried-out and shrunken cellulose sponge expands when dropped in water. If the entire board could swell and shrink slowly and evenly then this wouldn't be a problem, but because this is happening quickly only the ends of the board want to expand, while most of the length of the board stays the same width, and that prevents the ends of the board from expanding to accommodate the moisture. The resulting stresses begin to crush and permanently deform the wood at the end of the board. When it dries out again, those crushed wood fibers shrink, creating tension across the grain that is relieved by opening gaps at the weakest points, which typically means glue joint failure.

Another factor that could conceivably be contributing to this is the fact that you have many cutting boards. These cracks are caused by wetting-and-drying cycles, and the swings in moisture content for any given board might be wider because you are using each board less frequently, allowing more drying time between uses than you would if you only had one or two.

I have cut apart and re-glued at least one cutting board, but it's kind of a PITA and I always have enough wood around (I help run a student woodshop) that it's easier for me to just make a new one than to jump through hoops to rebuild an old one. I would not try to fill the cracks with anything, either; the repair isn't likely to last long enough to be worth the trouble. My primary recommendation is to avoid letting the boards soak in water. When you lean a board against the wall to dry, make sure it isn't sitting in a puddle of of water on the countertop, and turn the board sideways so that the grain is running horizontally and both ends are well-ventilated. Other than that, just live with it. A cutting board is just a tool, not a precious religious object. Use it until it's not useful, then grab another.
posted by jon1270 at 3:34 AM on January 3, 2017 [1 favorite]

Response by poster: Whoa. Thanks for the responses, all. Responses:
  • I guess I should have specified that these are not my daily cutting boards; rather these are carving boards. My daily cutting boards are all hard plastic, with different ones for meat and non-meat.
  • I also only have two carving boards, and the second one was a gift, also to replace the first one, more or less. To that end, I really only use one at a time; the other is sitting at the bottom of my drawer.
flabdablet is my hero right now. I'm gonna look into a single piece wood board, and I understand now how to dry my boards better.

Also I don't have a planer, so planing the board and regluing it isn't really a viable option right now. I guess I was hoping that there'd be a more simple fix so I didn't have to spend a bunch of cash and kick the environment in the pants a bit more (trees) but based on these responses, that's not really an option either.

Much appreciated, everyone!
posted by gchucky at 4:29 AM on January 3, 2017

Response by poster: Actually, a question: this site says:
if you used one large piece of wood, the board would eventually twist or warp. Because of the constant changes of water moisture in the air, all wood expands and contracts. This movement is what causes a single piece of wood to warp or twist. However, if you use the glue-up technique, the board will remain stable.
Is that true? If it is, it seems like there's a tradeoff with getting a regular (i.e. glued) board. With a single piece board, am I just going to have different issues to deal with?
posted by gchucky at 4:34 AM on January 3, 2017

Eh, it's sort of true but the explanation on that site is terrible. What's missing is that the way any given stick is prone to change shape, as its moisture content changes, is hugely influenced by the orientation of the tree's annual rings relative to the faces of the board. A "quartersawn" board's rings are perpendicular to the broad faces of the board, and such a board will tend to stay fairly flat even as it's moisture content changes. A "flatsawn" board has its rings roughly tangential to the broad surfaces, and will tend to cup one way or the other as its moisture content changes. Wide quartersawn boards are relatively uncommon and expensive because they can only come from large trees and the sawing process creates more waste.

Cutting boards are a good way for shops to use up the odd narrow strips that accumulate as leftovers from larger projects. The annual rings in those offcuts will be oriented every-which way, from flatsawn to quartered and everything in-between. If you were to carefully pick through the scraps, cut and orient them with the rings all similarly oriented and glue them together that way, then they'd behave pretty much like a board made from a single wide piece, being very prone to cupping if the rings were tangential to the broad surfaces, or exceptionally stable if the rings were perpendicular to those surfaces. But if you randomize the orientation of the narrow strips then when one board warps in one direction, it's likely to be compensated for by another board's warping in the opposite direction, so overall the board is likely to stay fairly flat. The glue joints are still a liability; that site's "wood chain" metaphor, claiming that a glue-up somehow makes each "link" stronger, is the sort of handwavey BS that I have no patience for.
posted by jon1270 at 5:00 AM on January 3, 2017 [1 favorite]

Also, I meant to comment that while most of Flabdablet's how-to up above is fine, the bit about using dowels between the parts is wrong. Dowels actually weaken this sort of joint.
posted by jon1270 at 5:07 AM on January 3, 2017

Best answer: A well-done glue joint is not weaker than the wood, it's stronger. But as jon1270 points out, grain orientation can undo you. One-piece vs. well-made glued up board should be roughly equivalent, but a lot of glued-up boards aren't super-careful about all the glued joints.

Your drying routine is problematic as mentioned above. If you're going to set the board on a corner to dry, do it on one of the sides, not the end-grain.

That crack looks too large to fix with CA glue (aka Super Glue), but very small cracks can be fixed with that. CA is thin enough that it'll wick into the crack, getting down to the bottom. You can then either rub the wet glue with sawdust to fill and cover the repair, or clamp the crack to try and push it back together.

If the cutting board is irreplaceable, get some sawdust of a similar color to the board on hand (possible by sanding the board a little). Fix the thinnest part of the crack with super glue, rubbing with sawdust to hide the glue-line as best you can, then fix the wider part of the crack with Titebond III mixed with the sawdust to make a putty-like wood filler (use a flat toothpick to push the filler into the crack - this is one of the few things in the world that flat toothpicks are good for) and clamp to push the crack together. You'll need to sand afterwards to clean up the surfaces. Then seal the board up with linseed oil, using multiple coats and allowing plenty of time for each to cure, as flabdablet recommends. With all the time for curing and drying, I would budget at least a week of evenings for the repair.
posted by DaveP at 5:13 AM on January 3, 2017

I agree with flabdablet and will also add that the board was glued together "wrong"
If you look at the picture, you'll see that the grain goes like this:
       ^glue seam
In reality, you want the curvature of the grain to alternate
       ^glue seam
which will help minimize problems with cupping (which is likely not what caused your problem, but it's better craftspersonship)
posted by plinth at 5:47 AM on January 3, 2017

Response by poster: Thanks for clarifying the one piece vs multiple thing.

Next question: why linseed oil over mineral oil? What about conditioners made from beeswax, or mixes of beeswax and oil?
posted by gchucky at 7:07 AM on January 3, 2017

Best answer: Linseed oil isn't better than mineral oil it's different.

Mineral Oil is a doesn't dry as such. it will not polymerize (form a plastic-like substance) over time. This is good for oiling cutting boards because it will stay a bit liquid in the wood and flow into cracks and scratches. It is also food-safe and won't go rancid or support microorganisms.

Linseed Oil is a drying oil, which means it will polymerize which will make the board more durable in that it protects the wood. It would be good as an occasional treatment. Flaxseed/linseed oil can go rancid so make sure you only use fresh oil. also make sure to use food safe versions of any oils you use.

If worried about meat & a wooden board, I just use a thin plastic board like this over my wood board to get the best of both worlds. https://www.amazon.com/Clear-Flexible-Cutting-Chopping-Mat/dp/B00BOUUX6G I will also spray my board down with a good antibacterial surface spray every night & let it sit while I was the dishes then I rinse the board clean & dry it flat so it won't warp (mine is on feet so it dries underneath not all are). I oil it with mineral oil every couple of weeks.
posted by wwax at 7:19 AM on January 3, 2017 [2 favorites]

As an alternative to dealing with splitting wood, you can also get a composite wood cutting board, which acts like wood in terms of cutting and lasting power, but doesn't warp & split like wood eventually will and doesn't need oiling. I swapped to these from Epicurean after losing yet another nice wood cutting board. They don't have the look and feel of wood, but I've carved a chicken and some smaller joints on the the gourmet series (has a channel running around the edge for juices and the like). Looks like they also have carving boards.
posted by carrioncomfort at 7:43 AM on January 3, 2017 [2 favorites]

A mix of linseed oil and beeswax is fine, but it's typically used for a delicate shining surface on non-varnished furniture. As someone said before, pure linseed oil hardens in a (for cutting planks) much-desired way (you'll have to take care getting rid of linseed-oil-soaked rags to avoid self-combustion).

Single-piece boards warp if the plank is cut from the side of the tree (slab-sawn). That's why I was opting for quarter-sawn wood further above. It is possible to get these, I have seen them on an artsy Christmas market only recently. I'm using one as my main cutting board: it has stayed flat as a tile for more than a decade.
posted by Namlit at 8:43 AM on January 3, 2017

you'll have to take care getting rid of linseed-oil-soaked rags to avoid self-combustion

I use mine to fire up the wood heater. They're good for that. And if they ever did spontaneously combust before I wanted them to, they're already in a firebox so no harm done.
posted by flabdablet at 8:55 AM on January 3, 2017 [1 favorite]

while most of Flabdablet's how-to up above is fine, the bit about using dowels between the parts is wrong. Dowels actually weaken this sort of joint.


Decent rationale here. If that reasoning is right, dowels would have a place when you're gluing endgrain to endgrain, but not sidegrain to sidegrain as for a cutting board or tabletop.
posted by flabdablet at 8:56 AM on January 3, 2017 [1 favorite]

Single-piece boards warp if the plank is cut from the side of the tree (slab-sawn).

I just checked my apparently-indestructible pine cutting board, and it's definitely slab-sawn; the grain swings around across its width, and runs parallel to the face of the board at the halfway point.

It warps a tiny bit, and it has one or two checking cracks. But as I said, it's 15 years old already and it's subject to completely vicious abuse.

It is in no way fine or beautiful woodcraft but it's a tremendously serviceable and very low-maintenance kitchen utensil.

A quarter-sawn board of the same size would have to come from quite an old pine tree in order to achieve the required width.
posted by flabdablet at 9:14 AM on January 3, 2017

Decent rationale here. If that reasoning is right, dowels would have a place when you're gluing endgrain to endgrain, but not sidegrain to sidegrain as for a cutting board or tabletop.

Yeah, he's making solid points, but it's even worse than he's suggesting. The reason dowels are actively problematic in a sidegrain joint, rather than merely unhelpful, is that they don't expand and contract in the same direction as the wood parts they are intended to help fasten, and thus they set up additional stresses that don't occur in a simple long-grain glueup. The longer the dowels, the bigger the problem. If the dowels bottom out in their holes or if the space between the end of the dowel and the bottom of the hole is filled with glue then when the wood becomes especially dry and shrinks to a size smaller than when it was assembled, the dowels have nowhere to go and cracking or joint failure becomes inevitable.

Similar hazards exist, albeit hopefully in smaller magnitudes, in many common joints where the grain of one part is perpendicular to the grain of another. This is just a case where such risks and stresses can be not only minimized but entirely eliminated. Aside from helping keep the parts aligned during clamping, dowels would provide no benefit at all in the assemblies we're looking at here.
posted by jon1270 at 11:31 AM on January 3, 2017 [3 favorites]

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