I learned it by using interlibrary loan to get a bunch of different partial resources and a university librarian to help me translate them. I'm sure youtube or something is an option these days.
The materials are available online. It is a very, very difficult skill. It involves a lot of experience and intuition with the mixing of many materials involved, plus a lot of spacial intelligence to fit the things back together correctly. And finally just tolerance for frustration because it often doesn't work, wasting hours of work and setting you back weeks.
If you like the aesthetics just use epoxy or something and gold dust. I can't really recommend it for the end result alone. Not worth the effort and frustration.
I just finished mending something dear for my mum.
I practiced few techniques on a cheap mug. In order to try out how the end result would look like.
From the photos and scarce info I got something to get me going.
I really don't like how the 'craft' method looks like - cheap western approximation of Kintsugi.
I wanted to get the look of smooth gold surface merging two pieces seamlessly. But also I want the gold line to be visible.
I couldn't really find info on what materials to use to acheive the original Kintsugi look, so I bought few things and started experimenting.
When practicing I noticed that when crack is clean there is barely space for golden seam. Also its hard to align pieces perfectly smooth. So the first thing I did was to file down the cracked edge with diamond file, at angle to preserve lower layers that will make contact and help align the pieces. This makes the crack gap appear larger, it makes it look easier and better looking in my opinion.
I ended up clear quick epoxy, to bind the pieces together. I used small amounts of it. When it was set but not dry i used a scalpel to cut out excess and make a groove in the crack. Then clean up the surface and let it set overnight.
Next I used slow setting clear epoxy mixed 1:1 ish with golden pigment (It was pure titanium oxide). I tried multiple pigments and the pale yellow seems closest to the really gold look. I filled in the gaps carefully making sure its barely above surface of the crack.
After hour or so when the epoxy mixture was gooey I used flat piece of wood with wet paper tissue to even out the surface. I pushed the 'spillovers' into the grove (for cleanup) and move the excess along the surface of the crack.
When that was all done, I clean off the surface next to crack and applied real gold leaf (its not too expensive, mine costed me €3 in total). Gold leaf is pain and I wasted some in the beginning.
The end result looks nice though not as good as the original pictures.
Can you comment on my technique and maybe give some info on traditional materials? Maybe recommended readings?
My advice is just to focus on getting them together correctly at that point and make sure the angles and curves are right. It's extremely difficult and there will be glue or resin everywhere but you can clean it up later.
A part of the traditional technique you might be able to use is how to apply the gold. They use a fine gold powder, but it isn't mixed into the resin. Once the crack is fitted and set it is painted over with resin again and then gold dust is sifted onto the resin before it cures. This ends up looking a lot smoother and better than leaf or gold mixed with the resin. There are some techniques where dust is embedded into it then sanded down but I don't recommend them for starting out.
Honestly it sounds like you're doing fine. That sort of experience is consistent with how I learned, it took about a dozen attempts before I got anything worth showing anyone. Like I said, it's a difficult, frustrating skill.
I might have few accidental breakages in the future :)
I find it quite relaxing and it could be my next hobby.
That said, urushi in all its forms is one of the most amazing art forms - there are literally thousands of decorative techniques and uses.
I'm not sure about immunity either though. Don't allergic reactions get worse with repeated exposure? I've always been careful about it for that reason.
I know some people who are very diligent about contact and manage to work without getting a rash. If you want to go that route you have to be very diligent. Apron, gloves, long sleeves, you don't need a mask. The problem for many people comes when their phone rings and they reach into their pocket (true story) or their nose itches. I am not that neat so I just went with it.
Are there any English language sites/communities dedicated to kintsugi that I should check out?
You can use cashew lacquer. It has its own pros and cons but isn't as nasty on the skin and overall easier to work with anyway.
Seems like it would be fun with (food-safe) epoxy and dye. One problem is that it seems like most glass-ware is tempered so when it does break it shatters in a million pieces.
The two seasons are worth a watch if you like this kind of documentaries:
Certified food safe epoxies exist but are expensive, e.g. ArtResin is one.
But some people will be satisfied living in plastic houses eating of plastic plates.