Repairing cracked ceramics

Let's explore different ways to fix broken pottery.


I broke my favourite mug a few weeks back.  Beautiful handthrown pottery by my favourite local potter.  All the pieces are there, actually, it's still holding together like a dented egg, but there is no way it will every hold coffee again. Not as it is.  I could repurpose it or use the materials to build something new.  But maybe it's possible to repair it and transform it into a functional mug again?  Or failing that, maybe I can patch it back together and use it for something else.


Kintsugi repair is a Japanese method using lacquer and precious metals.






If we ues gold or silver, the ceramic should be food safe and probably hold water.

Are there other methods for fixing broken pottery?  Pottery is such a wonderful material, easy to make local and far less energy intensive than glass and stainless steel.  Even still, I like to repair things when I can.

There are lots of chemical methods considered food safe by .gov that will stop a leak, but the Japanese method is the best I know.  

Can you tell me more about other food safe methods for repairing pottery?  This sounds like a very useful skill to have.

Food safe by government standards, not necessarily by mine or yours.

There are a few "food safe" super glues and plain lacquer.  There are also a lot of silicone products for the food industry that are made to seal a crack or seam.  I can't remember the name of the super thin stuff that wicked into cracks so well.  

Red RTV (room temperature vulcanizing) silicone from the auto parts store is supposedly food safe.  Not any other color, just the red.

I am not sure if you really need the gold to make the lacquer work, especially for a crack as opposed to a break.  I need to research this more myself.

I am not a fan of silicone for the fact a re-repair is nearly impossible, you can't get the original silicone out and nothing else will stick to it.  

i started a ceramic midden alongside the trail down to the stream. exhale, toss the broken bits onto the pile and move on.

Thanks for the link R Ranson. I've wondered how they do that for a while - lacquer makes perfect sense. I looked into lacquer a few years ago as a potential finish for my wooden ware, but decided against it because of the allergy issue and complicated curing. A small scale project like this seems like the perfect way to test the lacquer waters.

As to your question: I was always told by my ceramics teachers to use super glue. The regular really liquid kind (not the gel) will get into all those fine cracks. Make sure you don't leave any small crevices where food could get lodged & then go bad. It is food safe, but the repair won't look nearly as nice as gold or silver lacquer.

jennifer piddington wrote:i started a ceramic midden alongside the trail down to the stream. exhale, toss the broken bits onto the pile and move on.

this is me also...we've left a trail of broken handmade pottery behind for forty years...except for the gold/silver repair, I've never seen a 'repair' that satisfied the aesthetics of the piece.  It just always looked glued back together.  I had a 'pot garden' at our last place...spiders, toads, lizards and other crawlies loved it.....

In the back reaches of my memory, there seems to be something about using condensed milk to stick ceramic plates together. Can drag out any more than that right now though.

Sourdough starter works really well for glueing together broken pottery.  I don't think it's water safe though, so mostly only for dry goods.

I get this question all the time at my ceramics studio and the answer is always either give up on it or call Sotheby's.  If you're willing to pay 100's of dollars for ceramic repair on the clay level then go for it, otherwise accept the FACT that once broken, a ceramic body will never be healed into as strong and foodsafe a manner as its condition was.

David Miller wrote:I get this question all the time at my ceramics studio and the answer is always either give up on it or call Sotheby's.  If you're willing to pay 100's of dollars for ceramic repair on the clay level then go for it, otherwise accept the FACT that once broken, a ceramic body will never be healed into as strong and foodsafe a manner as its condition was.

That's discouraging to hear, but understandable.  I've been doing some reading and talking with potters and the only food safe strong method I've found so far is the traditional Japanese one.

One of the things I learned lately is that clay is a finite resource.  This is what I've heard anyway, and it seems correct.  It's unlikely we will use it up, but still, it makes me think about things differently.  I use to think, oh what's one broken mug, I'll go get another one.  Now I don't want that kind of attitude.  The more I learn about clay and pottery, the more I want to make the effort to preserve what I have - if not as a mug, then as something else beautiful and useful.  

A comment on the posts.  

Super glue works okay for decorative ceramics that don't ever do anything.  The advantages are seams show less, ease of assembly, minimal clamping(usually you can just hold it with your hands) and quick.  Disadvantages biggest is lack of durability if used.  Others include no real gap filling, poor moisture and heat resistance, too quick a set when assembling complicated breaks.  Now one other advantage that no other glue really provides is the wicking type super glue can be use to assemble a piece and then glue it.  Mostly you do you NOT want gels but most other super glues will work.

Epoxy is the most durable of the glue type repairs and is my preferred answer if the object is in use.  Some of the repairs made with epoxy 40 years ago are still in service in lower use items.  Epoxy is messy and seams nearly always show.  In most cases you want a low viscosity epoxy rather than thick to minimize this.  You can get colorants to mix with the epoxy to help hide the glue joints.(works well against solid colored objects especially in primary colors)  Epoxy is messy to work with and no matter how careful you are you almost always end up with glue some where you don't want it.  On the plus side you have good gap filling capability.  All of my long term epoxy experience is from before we worried about food safe.  Now from radiator shop experience know that normal epoxies start to soften about 220 degrees to 260 degrees.  So between that fact and the fact that epoxy like plastic gets hard and brittle over time this is usually what leads to joint failure.

The note about condensed milk is talking about making casein glue.  It is the strongest of the old time glues and is made from milk solids.  You can find hundreds of sets of directions for this glue on google.

Silicone sealant.  I have never used it for pottery but I work with it often in the shop situation and I have to agree with the poster on this.  Poor glue choice and nearly impossible to get rid of if you want to try anything else.  Should be the glue of last resort.   Because of the leverage that pottery pieces apply to the joint this one is virtually guaranteed fail.  Now if it fails getting rid of the silicone in a porous surface is nearly impossible.  If you have to do it best suggestion from shop experience.  Soak the pieces in a high volatility petroleum solvent like gasoline.(48 hours or longer)  The silicone will swell to 4 or 5 times its size and get soft and sort of gummy.  Scrape or peel as much as possible off then scrub the rest hard with an abrasive cleanser or use a sand/soda blaster on it.

Now that covers the ones I know anything about of the posted answers.  2 others I have used.
1.  Plain white school glue.  Not waterproof but easy to apply and okay in the more porous or lower fired ceramics.  High fire and not textured then don't even bother to try this one.  A poor ceramic that the break looks sort of like coarse sand in a decorative object so low stress and this one works fairly well.  Nice thing is easy to get rid of to try again.  Soak in water and scrub hard.

2.  Polyurethane wood glue.  I have one fairly coarse ceramic flower pot glued with this.  Wetted the pieces before gluing to trigger curing.  So far this is working and has been for years.  Don't know how it would work on glassier ceramics.

Now for any gluing of ceramics getting the joint clean is critical to any successful job.  If you just shattered it not a real problem but if it has been cracked for a while.  If most of the break is white but an area is brown with organic cooking type residues is the worst.  Getting that brown area clean is incredibly difficult.  Suggest throwing anything with this away.  It can take many harsh chemicals and hours of labor to clean such an area good enough for glue to begin to stick.  Another hard one to deal with is hard water deposits.  Common in broken flower pots that cracked over time.  Soak in acid like vinegar and scrub repeatedly till you get rid of all you can see.  I have done a couple of these that when the joint broke again it broke right through the hard water deposits.  The glue held but since it didn't stick to the ceramic but instead stuck to the hard water deposit that was what split.  Final wash in any case before gluing should be a residue free spray cleaner to get rid of any oils.

Finally getting glue on surfaces where you don't want it,  Especially epoxy, is common.  A cheap easy way to mask ceramics so the glue can't stick to the surface is to paint the surface with white glue and let it dry.  Then you can soak the glue loose taking the epoxy with it.  Painters paint on mask is another likely good answer here.  Tape is okay for smooth fairly flat surfaces but that is rarely where the break is.

http://hatoya-f.com/simple-kintsugi/for-kintsugi-beginner/


here's a how to for beginners.

please use google translate!
or ask a friend who can 日本語できる！
lol

i've had decent luck lightly taping the pieces together with scotch tape and the boiling the thing in milk for 10-15 mins. Brush milk onto the broken faces first before you tape them together. Let cool and dry and then pry off the tape.

Kept my favorite coffee mug alive this way for years before i finally shattered the thing into too many pieces to be salvageable.

One of the things I learned lately is that clay is a finite resource.  This is what I've heard anyway, and it seems correct.

As I recall from my geology days, clay made into a pot isn't a permanent change (in the geologic scale).  Given a few tens of thousands of years, vitreous (glassy) materials will eventually crystalize and normalize.  I realize given the lifespan of a human, 10,000 years seems damn near permanent, but I derive a little solace in the idea that our pottery will eventually revert, and eventually it may recycle and some vastly distant descendant might reuse it.

In general, I don't like to repair keramic things, I just throw they out. But sometimes we have memorable things that we want to live longer and that will be given to our children when they grow up. I guess, almost everybody has such things. And I'm no exception. So, thanks for the video!

Oh man, I broke my favourite cup first thing this morning.

Every time I see this cup it gives me joy so I want to use it all the time.  But now it's sitting on the table in four big chunks.

Abe Coley wrote:i've had decent luck lightly taping the pieces together with scotch tape and the boiling the thing in milk for 10-15 mins. Brush milk onto the broken faces first before you tape them together. Let cool and dry and then pry off the tape.

Kept my favorite coffee mug alive this way for years before i finally shattered the thing into too many pieces to be salvageable.

If you try this suggestion from above, please let us know how it works out!

I have a couple of Chinese claypots that i use for brewing traditional Chinese medicine. They crack if they used on too high a heat. All my pots are cracked because I am impatient! They are very difficult to buy in NZ so I make do and have to repair them regularly using garlic juice.  Fortunately I grow lots of garlic and freshly crushed garlic is very very juicy. I smear the juices over all the cracks, leave overnight to dry then boil a handful of glutinous rice with lots of water to make a congee (rice porridge). The starch in the rice water gets absorbed into the inner surface cracks. This pot has been repaired multiple times, it has garlic residue on the base from a winter repair when I had to use old fully cured garlic that wasn't very juicy and had to smear the crushed garlic over the cracks. Each repair lasts for several brews before the pot leaks again.

Amazing. I have three different pieces I have destroyed that I can now fix. I wonder, though, if one could use a goat milk-based paint as a sealant on the lacquer, or rather, what the specific requirements of the sealing layer are.

So gold and silver have been mentioned, which I would both use, but silver if I was doing it a lot, due to cost. Brass as well has come up as a metal powder option. Is anyone aware of any others? I have seen the repair in black, but I wonder if there's a powder coating there, or if that's just a lacquer finish.

Fascinating, though. I know a few ceramicists, and any work we get or are given is usually meaningful in some way. I would much rather repair than start a ceramic midden of my own.

Though the idea of a pot garden is compelling (get your minds out of the Cider Press, people!), much in the same way I find a rock garden is, but with a different character and potential for artistic exploration.

-CK

My husband wrote a heartfelt piece for our blog about the kintsugi method. He asked me what I wanted for Christmas, and I said I wanted my marble mortar and pestle repaired. The pestle had fallen off the counter and broke years ago, and I'd kept both pieces, hoping to get a kintsugi repair someday. Well, it turns out repairing with liquid gold is out of our price range, but Anthony came up with a great alternative.



Here's the full post, which is a great read, as he talks about the wider philosophy of that which is "broken."

https://www.catintheflock.com/2021/01/resist-bend-break-and-repair.html

Edwin Snell wrote:http://hatoya-f.com/simple-kintsugi/for-kintsugi-beginner/


here's a how to for beginners.

please use google translate!
or ask a friend who can 日本語できる！
lol

I can only read hiragana and katakana. And that is getting rusty. Context shore does help fill in the blanks. Which even helps in filling in the blanks so as to be able to read many Kanji.

I had a beautiful mug arrive as a Christmas present but got squashed in the mail.  I was thinking about this technique and there are a lot of kits available on amazon now.  But all the kits are NOT foodsafe and are only good to 100C.  Since I am at sea level, 100C is what my kettle boils at, so I'm sure it would melt the repair.

I'm going to get some surgru which is quite a bit cheaper and do the repair with that, and then use the mug for non-food stuff.  Sad, but there it is.  

Terry Byrne wrote:

Edwin Snell wrote:http://hatoya-f.com/simple-kintsugi/for-kintsugi-beginner/

日本語できる！

I can only read hiragana and katakana. And that is getting rusty. Context shore does help fill in the blanks. Which even helps in filling in the blanks so as to be able to read many Kanji.

日本語できる！ - Nihongo dekiru = Can you read/speak [depending on the context] Japanese? Literal translation - "Japanese can" [as I said intonation and previous context fills in the wider contextual meaning, even whether it is a question or reply]

When I first saw the title, my immediate answer was Kintsugi but I see
it is already answered. The Japanese have elevated this art to such a
degree that owners intentionally broke their ceramic vases to get them
repaired like this.

I repair broken pots discarded by my neighbours. I use hot-melt-glue
sticks and here are 8 examples of my handiwork:
111 Repaired pot outside the gate. Turmeric is growing in it. Passersby
      will ask for a few leaves once in a while.  I never say no.
222 On the nature strip outside the garden. The sunflowers growing
      in it were taller than I could reach. The pot has toppled several
      times. I was surprised because the seeds came from plants that
     hardly reached 2 feet high. At least 8 people have asked me
     for the seeds. I never say no.
333 Again outside the garden. Once that grass decomposes to the lip,
      I shall plant tomatoes. Like a shoemaker or tailor, I "advertise "
      in hopes of getting more folks interested in growing stuff.
444 A large pot embedded in a raised bed. I couldn't buy an electric
      garden shredder/wood chipper so what small bits I can cut with
     shears or jigsaw{it is a fantastic enabler for wood refuse. I should
     have thought of this years ago}. This is my testbed for wood chip
     gardening.  
555 Two large pots. The left is an overgrown Moringa which has
      toppled and broken the pot. The right is just composting until
     I can get more sunlight on it.
666 The largest pot I have ever repaired. It is sitting over the drain
      packed with grass clippings and a double turret for even more
     capacity. You can see that the bottom has given way but still
     usable for my purposes.
     In the foreground is a plastic pail with turret and at the
     back is another pot with turret. I dam the drain and pour kitchen
     sink water, laundry water and bath water through these to
     neutralize the chlorine with humic acid from the decomposing grass.
777 A broken vase which is on the waiting list to be repaired.

How do I do it? Well I start with two pieces. I squeeze three blobs
of glue along the edge - two at the extremities and one in the middle.
Sometimes 4 blobs as necessary. No fixed rules, just go with the flow.
I aim to leave a gap of about 1millimetre across the crack. I follow
through by injecting glue inside this crack from the exterior and interior.
If there are gaps, plant roots will enter and there goes all your work.
Finally, I tape around the pot with cloth tape and electrical tape and
wire for the big stuff. What happens when these give way or I
cannot find enough pieces? I break them into fragments with a hammer.
Along with 12-month aged humanure and crushed biochar, I  
have my own ingredients for Terra Preta. I have two threads here for
compost tea and biochar. Both are continuous and haltable operations.
Just search for ALL-B and ARS-C.

My encounters with broken flower pots and root balls and repotting
got me thinking about pre-broken flower pots. Imagine getting a flower
pot in 3 pieces that fit together like a 3-D jigsaw puzzle. Across each
"crack" or "join" are blobs/extrusions like broken off teacup handles.
You assemble the  pot by winding thread/string/twine around opposing
extrusions. As the plant outgrows the pot, you cut and recover the pot
for reuse. Isn't this good for the environment? Any potters willing to
venture into this untapped market?

So I have tried the milk method and it WORKS. I was skeptical, and there may be better methods with actual casein glue, but just regular whole milk bought from the grocery store worked well.

My Crock-Pot sprung a leak on the bottom and had a hairline break. It wasn't in two pieces, so I couldn't brush milk onto the broken edges, but I just submerged the bottom of the vessel in a large roasting pan and poured some milk inside to make sure the entire crack would be submerged. Simmered for a couple hours, I think (it was a little while ago).

Tip: I would keep an eye on it and stir if you want easier clean-up because the milk will create a film on top and cling to literally everything.

Months later, the Crock-Pot is still in use and definitely holds water. I also used the same method to fix a similar hairline crack in a mug handle. Harder to tell if that one really did anything, though. I plan to try it on a a chipped mug (still have the chip!) and a broken pizza stone. We'll see if it works on pieces that have fully come apart.

There is a fascinating show on BBC called "The Repair Shop" where they take heirlooms and repair them, commonly, these are ceramics of various types (dishes, vases, sculptures), but the program ranges from old toys and stuffed teddies or dolls to musical instruments, cabinets, trunks, signage, jewelery, furniture, leather goods and military memorabilia;  they seem to fix EVERYTHING...  
https://www.youtube.com/channel/UCLzG5rApQkTvO4JnBksPNaQ

Aside from the show being a delight to watch (and learn from; both the history of the item and the repair process), they do showcase a lot of ceramic repairs, one might learn something from it...

Most commonly, the issue with broken ceramics is previous, bad repairs and removing the adhesive completely so that the repair can be made properly.  The second issue is the use of "too much glue" that than oozes out, only to discolor greatly over time.  It seems the repair method is dependent on the type of pottery, and each type is done differently.  As to whether they are food safe when completed, I do not know.

I recently put a chip in the top of my sauerkraut jar, in the edge of the water trough. I usually thump the cabbage into the bottom to get the salt squished in using a wooden rolling pin. I sliced and chopped one too many cabbages and was determined to fill the pot to the brim, which meant I lifted the rolling pin slightly above the pot edge then thumped it not the cabbage.
So the chipped part, which I have, is not in contact with the food but as the cabbage bubbles it might touch, and now the water trough has only a skim of water or it spills inside. Since the point is to get a certain sort of growth I don't want the broken edge producing a breeding ground for the wrong sort.
I could repurpose the pot and buy another but I have yet to persuade myself the pot is dead! Will and epoxy join be foodsafe or not? I can't find one that says it is.
If I do get another pot it will be bigger so I won't try to fill it quite so full!!! Well, until even more neighbours ask for some :)

Here is an example of using black Sugru to repair a ceramic bud vase my son made. It leaked but I could not part with it. And also, here is an espresso cup whose handle broke and I repaired in this same manner with black Sugru.