> These days, some hobbyists opt for modern epoxy instead of the traditional and expensive Urushi lacquer. Epoxy probably yields a more robust bond and certainly allows for quicker repairs, but I question its safety for food-related use, especially at the temperatures found in a steaming cup of coffee.
People opt for epoxy because Urushi lacquer is traditionally made from poison oak sap and is a potent skin irritant to most people (it's where urushiol gets its name). It's really tough to do Kintsugi without smearing trace amounts of it all over the place, especially if you're doing it with kids, and cleaning it off is a pain since it's a hydrophobic sap. Even trace amounts can cause a reaction, especially if someone has sensitive skin or is severely allergic. People who do a lot of kintsugi develop a tolerance for it but it's an annoyance that most hobbyists just don't need.
Epoxies can be perfectly food safe and the FDA has a database [1] although it's not particularly user friendly. You can get MAX CLR or similar from Amazon. I wouldn't use it in an oven above 300F but it's fine for boiling temps. These FDA approved two part epoxies are used all over the place in hospitals and food manufacturing facilities where they're used to coat rough surfaces that would otherwise harbor bacteria.
I spent a few years messing with different approaches with epoxy but I never found anything that could replace urushi. It's really hard to get foodsafe epoxy to cure as hard as urushi, though I did eventually get one I was happy with. But the wheat flour in the traditional material pulls the shards together as it dries, and gives just an incredibly tight and strong bond that can really hold up to actual use of the restored vessel. Epoxy always weakens and fails after a while, while I have urushi/wheat/clay pieces that have been in daily use for years.
Depending on your goals though non-foodsafe epoxy can work well. Thickened marine epoxy, for under-the-waterline boat repairs is rock solid for decorative items. I'm sure it's toxic af and I wouldn't want it anywhere near my food but it would be fine for a lot of the things people want to do kintsugi for.
Cashew lacquer is also pretty cool. It's nowhere near as nasty as urushi and doesn't require a special environment for curing. If I were just getting into it now I'd probably start with that.
Hum... That can't be a coincidence. Both plants are on the same family. Let me check...
Yup, Cashew produces urushiol also. Unlike pistachos, cashew shells must be removed before selling the fruits for this reason.
So cashew plants can trigger skin allergies. Is a common family thing. Harvesting this things burn the workers hands. My bet is that would be also unsafe for people allergic to poison ivy.
I'm not a doctor/chemist, but as far as I understand, the polymerization of urushiol renders it hard and inert. Your thread discusses contact with raw urushiol as found in poison ivy, cashew sap (and apparently mangos) which is indeed known to cause allergic rashes in most humans. I'm not saying that kintsugi is definitely food-safe, but it's an important distinction.
Side-note: I did get some raw urushi on my fingers while working on this project, but nothing happened. Perhaps I'm immune.
> Side-note: I did get some raw urushi on my fingers while working on this project, but nothing happened. Perhaps I'm immune.
Somewhat the opposite. To be immune to it, your immune system would likely have to tolerate the authentication failure this substance causes after binding to a cell…which could be Bad in many other ways.
A likely explanation is that you removed the substance before an immune response could be mounted.
Molecules of the contaminant bind to skin cells around 15 minutes after contact. The affected cells are disrupted only in that they can no longer provide the appropriate response when challenged by an immune cell. When a cell cannot be identified as a member of the host, a chemical signal is released which tells killer immune cells to congregate and kill everything in the area.
This attack mounted by the immune system is the source of the irritation. It can be mitigated by antihistamine (somewhat), lower temperatures (somewhat, espeically on the verge of shivering), steroid injection (strongly).
Note that recontamination is the most common cause of "spread". Only a single molecule is enough to cause a reaction. Contaminated clothing and surfaces can still bear the oil after multiple washings.
> Side-note: I did get some raw urushi on my fingers while working on this project, but nothing happened. Perhaps I'm immune.
Might also be enough mechanical rubbing on fingertips during normal use that it mostly scrubs off. Whenever I feel it coming on from Urushi or accidentally touching poison ivy in nature, I rub it with water and course sand/dirt which seems to get rid of the urushiol.
I have sensitive skin so I start to itch shortly after contact and it builds from there. If I get it scrubbed off fast enough after exposure, I can usually prevent full contact dermatitis from setting in.
Urushi is more of a pain in the ass because its made from the sap, but Windsor and Newton artguard barrier cream seems to really help. Ideally apply it before use but it helps washing it off too if you forget.
A lot of people seem immune the first time. My mom thought she was immune to poison ivy, but after years of contact she became increasingly sensitized. Now she gets a rash of the cat has been walking through it.
I've never trusted that food safe epoxy actually is. I'm afraid that lobbyists have interfered, or its a situation where "there's no evidence that it's dangerous but there's not really evidence that it's safe", or the studies are funded by manufacturers, or there's something like manufactures pulled with BPA where they just switch to something functionally equivalent to a potentially dangerous chemical.
Is there any reason to believe that these epoxies won't just be like PFAS where in a few years the EPA/FDA will decide that they were actually risky?
You can even get (tobacco) smoking pipes decorated using urushi. It's made me wonder about the temperature stability, as a pipe can (but ideally shouldn't) get fairly hot.
Tsuge is a good brand to search for if you want to see exanples. Cost-wise such pipes start around the two hundred US mark.
This is really great results for an early project, none of my first few came out anywhere near so good.
I've been doing traditional kintsugi for about twelve years, a couple hundred successful repairs. Though when I started there was very little instruction or english-language resources available. It's become pretty popular for obvious reasons which is great for people getting into it now.
It remains probably the most difficult and frustrating skill I've ever learned. It's really hard to communicate just how meticulous, near-impossible some of the joins can be. There is a huge variety of technique and nuance to learn about different media and lacquer ratios for different kinds of joins & fills and it all needs to be done by intuition and experience.
And then the medium has no holding power until the curing process is well underway. So you need a lot of creativity to come up with a scaffolding system, pretty much completely unique to each project. Any problem after applying lacquer means hours of careful filing and rework, and more days or weeks of curing.
An edge-of-my-skill repair on a complete shatter takes about 100 hours spread out over 2-3 months. Even just an ideal three piece clean break is easily 8-10 hours and a handful of weeks.
Thank you for the kind words! I've not even scratched the surface of kintsugi of course, but the little I've learned agrees very much with what you say. It's a true test of patience.
Are you entirely self-taught then, or did you find a mentor?
Almost entirely self taught. I've got a few other practitioners I've asked for advice over the years but no one who really had guidance over my learning the way a mentor would.
Early on I got most of my info from the newberry library. It had a collection of illustrations and manuals donated from a defunct lacquerworks museum in japan, for some reason. They had someone around who even helped with a lot of translation for free which was a major help. All this stuff is available and better explained on youtube now though.
I’m working on a shattered teapot and am finding the scaffolding part very difficult. Any tips on holding pieces in place that you’d be willing to share?
Sure thing. For shatters the main thing is just accept that it'll take a while and plan on doing it one or two pieces at a time, ideally starting with the biggest and working down in size. I've seen videos where someone is fitting a whole shatter together in one go and holding it with rubber bands but this almost never works right in my experience.
A pair of good articulating arm clamps is my starting point for almost everything. I like to put the "main" piece directly under the shard that is being joined. You want the pieces as tight as you can get of course but you don't need a ton of pressure on there. The flour in the medium will draw it together some as it dries. If you get a good bond but it cures with gaps or holes in the join, you can fill in later with lacquer mixed with a fine clay. Tonoko or jinoko are the key words if you don't have it on hand.
Usually there's at least one join where you need to set multiple pieces at the same time. Sometimes I'll use a single string tied across the outermost shard to keep pressure on, usually across the rim of a bowl or cup. More than one string is too much to keep track of for me though. And the lacquer fumes are extremely detrimental to rubber and elastic, they will harden and break with a few hours of exposure so I don't use them at all.
A more traditional move is to bury the main body of the repair in a dish of sand, with the part to be joined exposed. Then arm clamps or whatever to hold the pieces together. Just make sure any joins that touch sand are fully cured. The cleaner you work the less sanding you'll have later. But there will always be some so do what's necessary to get it together then clean afterwards. I've even used masking tape to hold some many-pieced shatters together. It's a mess but it works, provided the piece doesn't have any texture or decorative elements that could be damaged by the sanding.
Good luck! It's the most tricky and frustrating part, and where most of the failures happen. You should probably expect some failures and setbacks, it's just part of it.
I've attended one of those at the Zen Center! My partner took me to one as a birthday present last year. She ended up being kinda frustrated with the process, but I found it soothing and relaxing, and left happy and contented.
The guy running the workshop had us use epoxy and not urushi powder (not surprising; I'm sure all of us would have ended up with severe skin irritation otherwise). The article mentions concerns about food safety; IIRC we were told that the epoxy we were using in the workshop was not food safe, but that it's easy to acquire food-safe versions of it.
We also didn't do this in anywhere near as many steps, with as many different treatments for different sizes/shapes of damage. Ultimately we fully repaired a piece in a couple hours, not the several months that the article author took to do it right. (And the extra care and use of the proper materials shows; the final repaired alligator mug from the article looks orders of magnitude better than my work.)
I wish I could offer something more useful, but in this case her birthday was fast approaching and I remembered her bringing up Kintsugi in a conversation. I did a search for "kintsugi toronto" and found that teacher's site on the first results page. Back in the day I would have browsed craigslist, but unfortunately it's not as popular here anymore.
Danger!!! Urushi is basically poison oak/poison ivy sap. Not quite the same, but in that family and with the same effects. Not to scare you off, but if you are interested in this, imagine all the things that can go wrong from if you were to get a tube of poison ivy sap and then do things with it.
That said, Urushi is great and the number of things you can do with it is truly amazing. Just don't do it rashly.
My wife recently got into kintsugi. She's learning the traditional method described here. I'm reading these comments with great interest and will be passing this onto her!
Most of the methods taught in the US are "gold relief" methods, which is basically glue with golden pigment mixed in. It doesn't look great but is modern and quick. "Gold flush" methods take a bit more time and are more authentic, but still don't use the traditional materials shown in this article.
Does anyone know where to get these traditional materials for use in classroom settings (i.e. in bulk, preferably discounted)? Not massive scale, just enough for a few classes. The kits have such a tiny amount and are so expensive, even a bulk discount of ~10-20% would be ideal.
When I was a kid I had a mug with my name on it that was gifted to me. My mother broke the ear off at some point and decided to glue it back on. A week later she handed me a steaming hot cup of tea and the ear tore off and I got severe burns on my leg as a result. Not great. As a result I am a bit wary fixing stuff meant to contain hot liquids
This is once again a perfect use case for cyanoacrylate. There's FDA approved, food-safe brands that will simply allow you to rebuild every fragment into the cup. It will also cure into ceramic in under a minute. I say this because I've done it. You're wasting time and energy using any other method.
I suppose it comes down to if you're purely in it for utility or if you're trying to repair this thing of yours precisely because it's this thing of yours. I'd be far more inclined to go to the lengths discussed in the article for a precious mug that I've used for a decade than I would for a mug I'd had for two, even if I'd still want to repair both out of thriftiness. It's a labour of love.
Honestly, using CA is what I and many other folks would use, in this situation. I’m a huge fan of J-B Weld’s Superweld light-activated glue. In the right lighting, you can see the steam puff from the glue when you activate it.
But OP’s process brings to mind the way we remember things: by reliving them in such a way that can (and usually does) produce a unique and slightly different product from the original. It’s the investment of time, thought, and love that makes this process more desirable.
I’m reminded of a recent comment thread on Jaloponik, where some great heads were talking about just _why_ the fact that anyone can go 0-60 in less than 4 seconds isn’t actually a great as it seemed to be. I’m a nutshell it came down to the fact that this used to be the product of untold hours spent learning and iterating to eke out tenths of a second, over time, to finally reach that level.
Admittedly it smacks of gatekeeping, but there is a fine line between gatekeeping and rewarding true mastery of an art.
Is it a good idea to use these as drinking vessels after repair? I always assumed the risk was too great. Even if you use some sort of epoxy over it, I would be concerned with contamination from the cracks not being fully sealed.
I recently broke a piece of glassware that had been with me for over a decade. I have all the pieces and I'm wondering if it's possible to stick it in a kiln and run a heat cycle that will cause all the cracks to flow together without deforming the shape, and barring that if there's a thin gold glue I could use to do some approximation of this technique but with cracks that are essentially zero width.
It is very thin, and will happily wick in and fill cracks. Often the join is completely invisible. The downside is that the cure time is on the order of 1-2 weeks. It does take a little practice to use effectively, and it's worth trying on less-important projects first, but it's straightforward enough that you can expect success if you follow the directions carefully.
I would seriously consider kintsugi for aesthetic reasons. You do not have to go with the gold thing. Basic urushi is black so you could go with just black. You can also get Urushi in quite a wonderful red. And there is truly spectacular orange.
As for the aesthetics. No matter what you do, you don't get a whole piece. It is broken and always will be. What you can do is to create something new that both has the beauty of the old and the care, beauty, whatever of continuing. I don't know how to explain this in logic, but there it is. I had quite a nice ceramic cup with charm that broke. I used black urushi which was not gaudy like gold leaf can be. I liked it even more than before.
Another option is silver leaf instead of gold depending on the glassware. And finally you can get really crazy. Rankaku is where you get little tiny pieces of quail egg shell and place it into the urushi. It is painstaking - to say the least- but the results can be beyond stunning. https://www.pinterest.com/pin/jean-dunand-18771942--55309901...
A very skilled glassmaker might be able to fuse the pieces together by heating the edges and pushing them together if the piece is simple enough but in general, no. That's why it's called glass blowing: the air pressure is what gives the glass form while it cools and vitrifies.
There is a method where you piece the glass together supported in investment, (a type of ceramic casting plaster), by building it up in layers. You tightly pack it and put it in the kiln, the investment holds the shape of the object when it melts.
This is a very advanced and difficult method of glass re-forming.
The BBC “repair shop” show recently (last year?) had an episode repairing a shattered vase with some specialist glass repair glue, so you can probably find some for this.
aside from 'the craft' and tradition of the process, is there any real benefit to using legitimate urushiol?
there are lots of bonding agents and epoxies out there that are not urushi based , actually food safe, and just as easily doused in gold dust, and completely compatible with prepared ceramics.
The author of the peace also mentioned that while there are food safe epoxies they were worried that they may be less food safe than expected when used with high temperatures like tea or coffee as opposed to being used in a simple serving dish.
Certified food grade epoxies are used in industry all the time; in fact, some wine is aged in epoxy-coated concrete tanks, and the inside of soda cans these days includes a thin layer of food-grade epoxy.
I will not fault anyone for not believing the certification, but I would personally want to see a more authoritative source than an undated ceramics FAQ. But this is just personal style! Being suspicious of regulatory thresholds is prudent.
(And this FAQ has me wanting to revisit my priors and research this a little more specifically, because its assertions are plausible, but need sources or explanations or dates, for cross-checking. Food-grade epoxy I believe in would be a handy thing to have exist; I do have some certified food grade epoxy in my garage that I haven’t used for anything yet and I’d dislike downgrading it to just “epoxy.”)
No worries, with Claude's assistance I came across the FDA's Title 21 chapter 1 subchapter B, specifically 21CFR175.300. You're welcome to see what the US government has to say versus some random ceramic site.(edit:tl;dr safety-tested food safe epoxies exist)
so are all the fixed up tea cups actually seeping stuff into the drink? I get that's always possible but a teacup is literally a container for near-boiling water
I’ve done this with a new and thus terribly sharp knife. I’d bought it for my mate, so when I knocked it off the bench my reaction was oh no! damage! catch!
The kitchen looked like a scene from Kill Bill. Perfect blood spray in an arc across the wall.
This mate lived with me at the time. And he was a nurse. He came home from his shift about half an hour later and I told him, sorry man, but you’re driving me straight back to the hospital.
I’m lucky to still have total use of my right middle finger.
Once, many years ago, I dropped a knife and caught it, fortunately by the handle. I felt very stupid for the obvious reason, but my cat was by my feet at the time--so I'm not even sure it was the wrong thing to do. Well, crisis averted, one way or another...
ITS POISON IVY! Do not breath in that stuff! I ended up the hospital with my face all bloated. No kidding. Japanese harvest from the urushi tree containing urison the irritant in poison ivy! I think they get off on shipping this stuff to American's laughing at them.
This is awesome! The handle on my favorite mug broke off recently. I tried super gluing it back on, but it broke off after a few trips through the dishwasher (hand washing got old). I was gonna try epoxy next, but I try to avoid that stank whenever I can. Maybe I'll give this a shot.
I have a bunch of kintsugi stuff in regular use so I can answer. Microwave is a definite no! It arcs, kind of like gold-rimmed plates would I guess.
Dishwasher you can. The repair is really two parts: the bond that holds it together and the gold dust that covers the lacquer. The join bond can handle the dishwasher. The gold layer needs touchup every few years anyway, but it will need it a lot more often if it goes through the dishwasher regularly. Gold is expensive.
There are some other ways of applying the gold that can hold up better, but they're less common.
People opt for epoxy because Urushi lacquer is traditionally made from poison oak sap and is a potent skin irritant to most people (it's where urushiol gets its name). It's really tough to do Kintsugi without smearing trace amounts of it all over the place, especially if you're doing it with kids, and cleaning it off is a pain since it's a hydrophobic sap. Even trace amounts can cause a reaction, especially if someone has sensitive skin or is severely allergic. People who do a lot of kintsugi develop a tolerance for it but it's an annoyance that most hobbyists just don't need.
Epoxies can be perfectly food safe and the FDA has a database [1] although it's not particularly user friendly. You can get MAX CLR or similar from Amazon. I wouldn't use it in an oven above 300F but it's fine for boiling temps. These FDA approved two part epoxies are used all over the place in hospitals and food manufacturing facilities where they're used to coat rough surfaces that would otherwise harbor bacteria.
[1] https://www.cfsanappsexternal.fda.gov/scripts/fdcc/?set=Indi...