Repairing Cracked Earthenware: A Safe Solution for Culinary Use?

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EnumaElish
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How can I put back cracked earthenware (coffee cup) in a way that would not be damaging to continued culinary use? I doubt that superglue is healthful or tastes good. I need at least one out of two. Any suggestions?
 

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1] Superglue is used directly on skin to close wounds; health is not a problem.
2] Anything you use will need to offgas anyway to rid it of any residual taste before using.
 
I have found, that earthenwear pottery doesn't hold up well in use, once you glue it. Coffee cups more so with much heat expansion problems.
 
i don't think its very fixable. once cracked, there's the po tential for germs to get in the cracks, even once fixed up, and then its hard to clean those germs out, and then you get sick whenever you drink your coffee. and I'm pretty sure you can't rebake pottery that's already finished. the glaze that's on it would burn.
 
I would put in the best possible epoxy I could find. Rebaking it wouldn't do anything because the new clay wouldn't bond as well to the hardened clay.
 
Ok... by "earthenware" do you just mean ceramic? Is it already fully baked? Is there no glaze on it?

If it isn't glazed you probably shouldn't be using it for a coffee mug anyway. If it has been baked even once I don't think there is anyway of repairing it unless it has been glazed too in which case you can probably use an epoxy or superglue. Even if it is glazed though if the clay is really porous or relatively low grade it will likely just break again. Low grade clays have a tendency to not want to take glues very well. If it's a finer higher quality it will be much more solid and fixable.
 
Here, at least, you can buy porcelain repair in a bottle. There are 2 different kinds, as far as I know. One is for just the sort of thing that you're dealing with, and the other is for touching up bathtub or appliance surface chips. I don't know if the glue type works well on rougher types of pottery, but it's great for teacup handles and the like.
 
Danger said:
Here, at least, you can buy porcelain repair in a bottle. There are 2 different kinds, as far as I know. One is for just the sort of thing that you're dealing with, and the other is for touching up bathtub or appliance surface chips. I don't know if the glue type works well on rougher types of pottery, but it's great for teacup handles and the like.
You gave me a reason to be optimistic again! Do you know commercial trademarks? Or who produces them? I will look them up if you can tell me who makes them.

It's fully baked and glazed, fine earthenware -- not ceramic -- at least I don't think it is ceramic.
 
moose said:
I would put in the best possible epoxy I could find. Rebaking it wouldn't do anything because the new clay wouldn't bond as well to the hardened clay.
Do you think Araldite is a good epoxy for this? Or should I look for hard waterproof epoxies, like Titan? (See the surfboard picture on https://www.physicsforums.com/newreply.php?do=newreply&p=872683 , it's pretty amazing.)
 
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Enuma, I think that it's just LePage's. I don't live at the same place where I left the stuff, but I'll do some snooping and see if I can come up with it.
 
EnumaElish said:
It's fully baked and glazed, fine earthenware -- not ceramic -- at least I don't think it is ceramic.
Any natural sort of clay that has been fired is a sort of ceramic. Earthenware is a particular type of ceramic.
I took a couple of ceramics classes and my terminology is starting to come back to me. I thought you were referring to bisqueware which is unglazed ceramic only about half fired and waiting to be glazed. Most ceramics I have seen labeled earthenware weren't glazed at all, the reason I confused the two, so I was worried you might be trying to use unglazed ceramic for a coffee mug lol.

Anyway, if it's a finished product then it should glue pretty well. I have not ever used the product that Danger mentioned but it sounds like a good idea if you can find it. It should be better since it is made specifically for repairing finer grade ceramics. Ceramic is notoriously difficult to get to glue well.
 
http://www.krazyglue.com/prac_krazy/prac_krazy.asp?catID=7&subcatID=30&prodID=33

Super Glue/Krazy Glue apparently make glues for fixing porcelain and cermics.
 
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Found it!
http://www.lepageproducts.com/products/detail.asp?catid=21&subid=52&plid=270"
You can probably order it from your local hardware if they don't normally stock it.
 
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TheStatutoryApe said:
Any natural sort of clay that has been fired is a sort of ceramic. Earthenware is a particular type of ceramic.
I have just realized that I meant "It's not china" when I wrote "It's not ceramic." (China Ware is advertised to be good for ceramics in general, so I am hopeful that it willl work. Thanks, Danger.)

And, happy birthday, Statutory Ape!
 
You might be able to glue your cup back together if it has special meaning and you want to keep it, but I wouldn't try using it once cracked. It's just not going to hold up, and as Gale mentioned, it'll be difficult to clean since it won't have a glaze on it over the crack, and if you're pouring hot liquids into it, it's going to be prone to re-breaking. So, if it's more broken than just sticking a handle back on, I'd recommend just buying a new one.