Ordered 20 replacement single-convext yunzi stones from YMI. The stones that arrived are noticeably smaller than the ones I have. I thought for a second maybe I have Chinese-sized yunzi stones, but I doubt it, because a) I received a confirmation in the past that directed to a page that said “Japanese-sized”, b) my old stones fit my Korean boards perfectly.

So, does anyone know if YMI reduced the size of their stones? If not, would it make sense that I might have Chinese-sized stones? In that case, anyone can recommend a place to get some more Chinese-sized yunzi ones (of the new variety, with whiter shade of the white stones)? I am having trouble finding those online in the usual English-language places (Amazon, YMI, etc.), although I am sure there are plenty Chinese-sized yunzi stones available.

Attaching pictures (new stones in the center on one of them, to the right on the other, next to my old stones).

Contact them and see what they say.

Seems unacceptable.

They replied and said that that “batch sizes are not uniform” and asked to send a picture of my old and new stones next to a ruler. Seems very weird, product quality-wise.

A side effect of me looking up where I can buy Chinese-sized stones or whether someone had a similar experience to mine was that I realized that these stones still contain lead. I was under impression that issue had been resolved, but apparently not completely. I like the stones, but not enough to endanger my health (and especially that of my baby).

Get a caliper and get very accurate measurements of your original batch vs. the replacements.

That's terrible.

Plus the lead issue.

Yes, the lead issue is a gamechanger for me. I don’t want to play with yunzi material anymore, despite liking its feel and appearance.

But then, when I looked up melanine, apparently, it’s also pretty harmful. Are there no safe single-convex stones? Can one buy ones made of clay or something?

I am not troubled by lead in yunzi stones, science is quite clear about this
so, as far as you don't eat your stones it is really nothing you have to worry for
btw, sorry for the OT, this is only my opinion, also if I studied some toxicology
(let's say that, so far, that's more toxicology than Go )
Galation

_________________
When you play Weiqi you are joining millions of people across four thousand years of time.
Jonathan Hop - So You Want to Play Go?

lead oxide is used as an agent to lower the melting point of the molten glass to make it easier to work with at lower furnace temperatures.

Exposure through skin is also possible. I have no idea what amounts result in what exposure, and there is no controlled third-party systematic test for lead contents at the moment. I am definitely not going to trust any internal reports done by a Chinese government-controlled factory (no offense to anybody Chinese; I am from Russia and the same goes for any East European government-controlled factory; governments outside of the West don’t take individuals’ health very seriously, without getting into too much politics). And anecdotal evidence from various users on the net suggests much higher levels of lead than what YMI’s internal reports suggest.

If someone purchased ten batches of stones, randomly selected ten stones from each, and showed results from a Western lab, and then explained why the reported amounts are safe to be chronically exposed to through skin, I’d change my opinion.

One cigarette won’t cause cancer, but years of even second-hand exposure build up. I just don’t need that sort of danger for myself and my little daughter for the sake of playing with nicer stones.

Sorry to insist. The info about no skin exposure for the inorganic lead compounds is correct, scientifical based and connected to the case of the yunzi stones. The difference between toxicity and carcinogenicity is also substantial, especially to determine a "safe exposure level", a concept that is near nonsense in the latter case.
Please consider that sugar (C6H12O6) and salt (NaCl) have a known toxic level (Lethal Dose 50% = 0,6 kg for sugar and 0,4 kg for salt).
I don't want to be a wet blanket but, anyone tested glass stones for lead content with the kit?

Anyway, I can fully understand your No Risk Policy about your daughter, especially if 0-3 years old
Galation

_________________
When you play Weiqi you are joining millions of people across four thousand years of time.
Jonathan Hop - So You Want to Play Go?

those stones on the right do look smaller