Chemical/Paint Any ideas about food safe glues for cracks?

[Rive]

TL;DR Summary

Ideas needed to fix up cracks in ceramics

Some of our ceramics dinnerware started to develop cracks. They are still in one piece, but those cracks are not exactly good to look at.
And, of course they are not exactly hygienic either.

So I started to look for some liquid glues to stabilise them and fill up those small cracks.

There are many hits either for glues for ceramics repair, or food safe glues, but the catch is: so far I could not find a single product where the manufacturer (not the shop!) properly declares the product food-safe. Dishwasher-safe - yes. Waterproof - yes. Pictures about a cracked mug glued - yes. Shop listing it as food-safe - yes.

But not a single liquid one (so far) where the manufacturer declares it food-safe.

Any ideas?

 

[jedishrfu]

Get new plates rather than risk using an untested product.

 

[Rive]

Yeah, I could find some quick&dirty solution anytime, for cheap.

The issue is exactly that despite all the hints on the packagings there seems to be no product which would be actually proper for the task

 

[fresh_42]

If the glue is neither soluble in water nor in oil, how likely is it that it diffuses into food?

 

[jedishrfu]

Microwave maybe

 

[fresh_42]

Microwave maybe

Of course, it has to get its time to evaporate. I just think that the potential danger is marginal compared to all the other risks that we daily take without mention: phthalates, benzene, formaldehyde, acrylamide, etc. A small crack in a pot is nothing compared to all the plasticizers used in wraps, burnt oil, fried salt, etc. And last but not least: acetone in nail paint removers.

 

[BillTre]

There are also UV cured glues.

Also, the usage will affect potential contamination. High temperatures and different pH's will affect how easily any bad substances in the glue might be released in to your food.

Personally I like the "get new dishes" idea.

 

[bdrobin519]

If the glue is neither soluble in water nor in oil, how likely is it that it diffuses into food?

Possibly microwaves could induce leaching.

 

[Baluncore]

If the glaze cracks, but the underlying ceramic does not, then you have a thermal expansion coefficient difference between the glaze and the ceramic base material. That should not normally be a problem, but it might be aggravated by using the ceramic plate in a microwave. Then, the differential heating may be more rapid, due to differences between the glaze and the ceramic.

Super-glue can be used to fill the cracks in the surface glaze of ceramics.

When ceramics break, epoxy will put the pieces back together. When using epoxy to repair ceramics, clamp the fragments tightly together. I use many strands of electrical PVC tape under tension, to close the gap, and squeeze out all excess glue. The gap will often close and hide the joint, with the grains along the break, interlocking again. Thick epoxy does not look good, and will not last, as it behaves differently to the ceramic in hot water.

Any organic glue will fail after exposure to high temperatures. Both epoxy and cyanoacrylate based superglues fail at about 150°C. That may be OK in boiling water, or a dishwasher, but not dry in a microwave, where the epoxy may exceed safe temperatures. If the temperature exceeds 150°C, the organic glue will release reactive toxic molecules and monomers.

If the ceramic tableware has sentimental value, mount it in wire frames and display it.

Either way, replace it with a microwave safe product.

 

[jedishrfu]

Maybe dental glue would work. They use it to cement crowns onto tooth roots.

 

[JT Smith]

Dental adhesives may not be designed to withstand cycling temperatures above, say, 60°C. Maybe if you kept the food cool and hand washed them?

I'd personally be worried less about food safety. The most stringent food safety approach rules out glazes with crazing or anything that has unglazed clay, regardless of how well vitrified. The idea is that any chance for intrusion by water and bacteria makes it inherently unsafe for food. That's a pretty hard line and not likely to present a serious concern in practice, provided you wash your dinnerware well. But if you're the type that puts safety first rather than third then any joined surface would be suspect.

Additionally, at least with larger items like plates, I'd be worried about a join failing suddenly and unexpectedly in the future, perhaps due to weakening of the adhesive with time, temperature, mechanical stresses. I have a scar from a plate that broke while I was hand washing it. That one had a small visible crack in it so I was an idiot for using it (for years) like that. But with an adhesive joined crack you'd have the same basic issue.

A scar is something that I'll carry with me and remember. Food poisoning? Most of the time you can't really be sure why your GI goes off the rails for a few days.

 

[Rive]

If the glue is neither soluble in water nor in oil, how likely is it that it diffuses into food?

Plastics is either not soluble in any food, but they are still a concern - up to the point that food-grade plastics were born.

Microwave is no concern. Nothing particular against it, but we prefer proper cooking, so we just did not buy any of those warmers.
Also, the expected temperature range is limited at the range of dishwashers. No concern here.

There are also UV cured glues.

Good idea, but I don't think they could properly cure deep in the cracks.

New dish - well, I just hate to throw away usable stuff without a fight.

Super-glue can be used to fill the cracks in the surface glaze of ceramics.

They are deep cracks (through the whole body) but still just cracks and the dish is in one piece (so, no epoxy yet).

Super-glue variations were my primary search direction so far, but not a single one I've found was declared food-safe.

Maybe dental glue would work.

Thanks, but same as epoxy. Not applicable for those yet small cracks.

I'd personally be worried less about food safety.

I tend to worry about food safety far less, but I also prefer doing proper job and consider kludging only when other options depleted already...

 

[JT Smith]

I tend to worry about food safety far less, but I also prefer doing proper job and consider kludging only when other options depleted already...

With all due respect, and coming from someone who likes to try and repair stuff when possible, I think that repairing a plate for functional use is in itself a kind of kludge. Keeping the plate 100% food safe in the process is basically impossible unless you can refire it so as to seal it in a food safe glaze.

Use it as is or kludge a repair, either way it's less than optimal. The best approach is acceptance: It's toast. Buy a new one.

 

[DaveC426913]

If the glue is neither soluble in water nor in oil, how likely is it that it diffuses into food?

Solubility may be less of the issue than straight up physical crumbling and disintegration.

 

[fresh_42]

Solubility may be less of the issue than straight up physical crumbling and disintegration.

I still think that it is negligible compared to all the environmental chemicals we are exposed to anyway. I listed the standard exposures in post #6. A bit of instant glue would not make a significant difference in my opinion.

 

[DaveC426913]

I still think that it is negligible compared to all the environmental chemicals we are exposed to anyway. I listed the standard exposures in post #6. A bit of instant glue would not make a significant difference in my opinion.

Well that's true.

Although I would separate out things like nail paint removers, since that's not something we would normally put in direct contact with food that we are about to put in our mouths.

 

[fresh_42]

Well that's true.

Although I would separate out things like nail paint removers, since that's not something we would normally put in direct contact with food that we are about to put in our mouths.

Depends on your gender or personal habits. And you need acetone after you've glued the cracks .

A bag of chips is more dangerous. (acrylamides)

 

[DaveE]

- UV cured epoxies are used in dentistry. They don't buy it at Home Depot though.
- Cyanoacrylates are use in surgery. They don't buy it at Home Depot though.
- Silicon is used in fish tanks.

I might be concerned about what else the manufacturer puts in their product beside the main ingredients (they all do this, I think). Anything can kill you if you have too much exposure, but I doubt we could tell you about the hazards of trace exposure.

None of these applications has large temperature cycles like cookware. My limited experience with resin cured epoxy and cyanoacrylate is that it will fail.

Then there's gold (and lacquer), used in Kintsugi. It's beautiful, but can't be used for cooking.

The only repair that I think might be durable is a glass frit process, which basically requires refiring the dish in a kiln. Kind of like welding, but with glass/ceramic. Honestly, it's the only good way to join ceramics. But I've never heard of it being used in one-off repairs.

If it's worth keeping, I'd use superglue and put it on a display shelf. Otherwise, give up and replace it before it breaks all the way.

 

[BillTre]

- Silicon is used in fish tanks.

I might be concerned about what else the manufacturer puts in their product beside the main ingredients (they all do this, I think*).

Lots of stuff gets added to these kind of things.
WRT aquarium silicon, it is different from the silicon used for sealing windows and other household projects. They usually have fungicides which are toxic to fish. There are special fish OK silicons sold, but not usually at Home Depot type places. On-line fish suppliers are usually the place to look for them.

Same goes for a lot of products. You can get them but it takes a bit of work and knowledge (you have to know what you are looking for before you can find it (AKA Google-Fu)). There is, for example, an on-line supplier of epoxies that probably sells about 500 different products for many different purposes.
Therefore, I like industrial suppliers.

 

[Tom.G]

Here are a couple articles on ingesting Superglue. The 2nd one says if you eat and/or swallow it (before it cures), right away you should call either the national emergency response number (911 in the USA), or the Poison Help hotline (1-800-222-1222 in the USA).

https://www.poison.org/articles/super-glue
https://medlineplus.gov/ency/article/002894.htm

Other articles point out that if you get Superglue on a large area of skin, the heat it generates while curing can cause burns. Also, there is a Surgical version of it that is sometimes used.

Several 'un-official' articles state that Superglue is non-toxic after it cures.

Be aware that many (most?, all?) Superglues are brittle when they cure, so watch out for temperature swings which can cause differential expansion or contraction.

One place I worked used Superglue to hold accelerometers on equipment during vibration testing of military equipment. The accelerometers were mounted on small metal blocks and the blocks were glued to the test object. After the testing, the metal blocks were tapped with a small hammer and they flew right off, ready for the next project.

(above-referenced sites found with:
http://www.google.com/search?hl=en&q=is+superglue+toxic)

Cheers,
Tom

 

[JT Smith]

In addition to mechanical issues Superglue doesn't do well at higher temperatures. Heat is an alternative method of breaking the bond when it isn't possible to get acetone into the joint area. I would imagine that cycling it even to dishwasher temperatures would degrade it over time. But maybe that's just my imagination. You could test it.


Gorilla says: "Gorilla Super Glue can typically be exposed to temperatures ranging from -55° to 100° C. Too much exposure to water, especially warm water, can compromise the strength of the bond."

 

[Rive]

Several 'un-official' articles state that Superglue is non-toxic after it cures.

At the end it'll be an 'un-official' superglue variation specially for ceramics, and with a broken mug on the packaging.
Still without the 'food-safe' declaration, though.

 

[JT Smith]

Well good luck. If it poisons you in some small way it will be virtually impossible to know but it would be interesting to learn how long it lasts before the repair fails.

Have you decided if you are going to put it in the dishwasher?

 

[Rive]

Have you decided if you are going to put it in the dishwasher?

I'll see how it goes first. If the crack sucks up enough glue to show up on the other side (so that the whole width will be connected) then I'll think about it.

Preparations will take some time. Wash it several times (dishwasher), then dry it for some hours so that the crack will be completely dry and clean...