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I recently came into possession of a wonderful turned maple bowl however there is one downside. There is a small crack about halfway through the bowl. The crack goes fully from top to bottom but not fully left to right. The bowl is not about to fall apart but I think after a while of putting fruit into it, or several used as a salad serving bowl the crack would spread and weaken.
Is it possible to glue this and (bonus points) glue it with a food safe glue?
I suspect that it actually isn't going to get any worse. However, what is generally accepted practice is to use epoxy. If you want to hide the crack and patch you can mix in some sawdust, in this case maple sawdust would be best. As an alternative, you could mix in some other colorful stuff to make it pop. Ground turquoise is a common choice for this.
Of course any glue or epoxy will leave a bit of a mess and will need to be cleaned up. You might end up needing to refinishing the whole piece. If that is the case, nut oils are food safe and so is carnuba wax, which is hypoallergenic.
If it were mine, I think I'd either try a tinted epoxy or epoxy-based filler. Or I'd accept the crack but stabilize it with a butterfly inlay... or just accept the crack as part of the character of the piece.
Frank Howarth made a great video about how he "repaired" a cracked wooden bowl.
The rough turned maple bowl that I wanted to finish next had cracked. The crack was at an angle to vertical when the bowl was sitting normally. I cut out the section of the bowl with the crack on the band saw. Then I build a new segmented piece to take the place of the section. In this new section, I continue the idea of the chevron pattern, and add more detail. I give the chevron pattern branches by adding alternating pieces of birch and walnut wood on either side of the pattern. I also add a walnut ring at the top of the bowl so the segmented pattern has something to die into. Then I turn the whole bowl down to a finished piece.
He made a feature out of it
You'd have to be ambitious to do what he did but it might serve as inspiration.
Due to the size of the crack a mechanical repair would be best like the aforementioned butterfly or stitch inlay or in lieu of that an epoxy would work. I wouldn't try to color match with dust or pigment as it just plain won't match and may just become an eye sore. If you want to color it go with black or some sort of metallic mix. CA glue, aka super glue, probably won't work here - it's too large of a crack. I wouldn't do it on my bowl. Filling it with gap filling or thick CA will probably result in a mess, also CA glue is brittle while epoxy can flex a little bit with seasonal movement. I use CA glue for hairline cracks, not open, through cracks. And you would never clamp this back into place - there is a reason it split in the first place so don't force it back. (Shrinkage, seasonal movement, too close to pith, internal stresses, etc)
For the epoxy generally almost any two part epoxy would do. Using blue tape, tape off one side of the crack so it doesn't just spill out all over. and fill. After dry remove tape and sand bowl or at least the local area and refinish with mineral oil, wax or a combo of those or walnut oil. Boom you're done.
Since the surface would need to be cleaned up manually (not on a lathe), try CA glue and clamp it together. Much less mess than epoxy to clean up. The CA glue will be safe after fully curing.
Not enough rep to add a comment but most glues are food safe when dry. The drying agents may have toxins in them but they evaporate and the dried glue is okay. Obviously you'll want a glue that's waterproof when dry such as Titebond III
The Wood Whisperer has a good post on this
You might want to get the "gap-filling" variety of CA. It's nice and runny and should seep nicely into the void without a lot of coaxing and, of course, as the name suggests, it will fill the gap. Personally, I wouldn't bother with clamping which will just put undue stress on the glue. If this crack had been in the bowl when the turner was making it, he/she would certainly have patched it in this very manner. It probably developed after the wood continued to age/dry-out after the finish was completed. You are just trying to get something to patch the opening. You can find it at the big name woodworking stores and online.
