Warning, Yunzi Stones Are Dangerous To Health

[Tyvex]

Hi all,

I know this thread is a bit old, but I thought you all might be interested in an update. I received a set of yunzi stones as a gift at the end of 2013, and, upon reading this, tested mine with an at-home lead check from 3M. The results were inconclusive, so I sent the one broken stone included in my set to Schneider Laboratories Global (http://www.slabinc.com/) to have it tested professionally.

I recently received the results in the mail, and I thought I'd share with community. Here's a link to a photo of the results: http://i.imgur.com/0azOoi7.png

In short, SLG found only 3 ppm of lead in the stone I sent. This is far below the 90 ppm limit set by the Consumer Product Safety Commission.

This doesn't prove that all yunzi stones are safe (or even necessarily that all of mine are), but it certainly supports YMI's claims.

[TKP]

Thank you for this information. If you don't mind me asking what color was the stone you had tested? If you read Chiyo Dad's website it sounds like lead was only a problem with the white stones.

[Tyvex]

Thank you for this information. If you don't mind me asking what color was the stone you had tested? If you read Chiyo Dad's website it sounds like lead was only a problem with the white stones.

You're quite welcome. As it happens, I tested a white stone.

[Pericles]

Hi,


Lead was supposedly abandonned a decade ago, thanks to the http://en.wikipedia.org/wiki/Restriction_of_Hazardous_Substances_Directive (RoHs) european directive. As an ex-electronics worker, afaik, there is nothing proven about it being so "unhealthy" except of course, if you eat your stones.
It's just the same as with painting. If you let your kids eat pieces of your walls containing "pieces of lead", of course they might be sick. And I say "might" because even that is still under debate.
The RoHS directive was more an environment directive than a health directive. Health was used as a pretext to validate this law (until further proof that it had consequent impact on health). I'd like to add, any ingestion of product, in great quantity possibly has an impact on health, be it stain, copper or anything else.

I don't think you should worry about it, generations of people relied on lead-based painting for their walls, and truly, I'm still waiting for scientific proofs to corroborate any fact between sick people and the fact lead was used.

Pericles

[RBerenguel]

Hi,


Lead was supposedly abandonned a decade ago, thanks to the http://en.wikipedia.org/wiki/Restriction_of_Hazardous_Substances_Directive (RoHs) european directive. As an ex-electronics worker, afaik, there is nothing proven about it being so "unhealthy" except of course, if you eat your stones.
It's just the same as with painting. If you let your kids eat pieces of your walls containing "pieces of lead", of course they might be sick. And I say "might" because even that is still under debate.
The RoHS directive was more an environment directive than a health directive. Health was used as a pretext to validate this law (until further proof that it had consequent impact on health). I'd like to add, any ingestion of product, in great quantity possibly has an impact on health, be it stain, copper or anything else.

I don't think you should worry about it, generations of people relied on lead-based painting for their walls, and truly, I'm still waiting for scientific proofs to corroborate any fact between sick people and the fact lead was used.

Pericles

The RoHs seems to be binding only for the EU. The Asia-Pacific section (with the "China-RoHs), states that China works differently and this only applies for electronic equipment... Which Yunzi stones are not.

[Pericles]

Not just electronics in fact. Afaik, it applies to every lead-based material. Maybe i'm wrong about that, I didn't check. Still doesn't change my point though, unless you eat the stones, it should do you no harm

[RBerenguel]

Not just electronics in fact. Afaik, it applies to every lead-based material. Maybe i'm wrong about that, I didn't check. Still doesn't change my point though, unless you eat the stones, it should do you no harm

The RoHS directive took effect on 1 July 2006, and is required to be enforced and become law in each member state. This directive restricts (with exceptions) the use of six hazardous materials in the manufacture of various types of electronic and electrical equipment.

Emphasis mine. I agree that unless you swallow them, the risk is very minor. The thing is, touching the stones and then touching your lips, or eating while playing, or... can actually be a moderate risk. With long exposure, a relative risk, after all, lead does not go away, it just accumulates on human bodies.

[xed_over]

The thing is, touching the stones and then touching your lips, or eating while playing, or... can actually be a moderate risk. With long exposure, a relative risk, after all, lead does not go away, it just accumulates on human bodies.

I seriously doubt it.

[RBerenguel]

Depends on how easily lead leaves the surface of Yunzi stones. In any case, I wouldn't risk it if possible.

[Bonobo]

The thing is, touching the stones and then touching your lips, or eating while playing, or... can actually be a moderate risk. With long exposure, a relative risk, after all, lead does not go away, it just accumulates on human bodies.

I seriously doubt it.

Doubt is A Good Thing™, doubt and curiosity are what drives science

Wikipedia —> Lead —> 7 Health Effects

And the next chapter, 7.1 Biochemistry of poisoning, begins with

Exposure to lead and lead chemicals can occur through inhalation, ingestion and dermal contact.

“dermal contact” … skin contact.

Yes, this is Wikipedia, but it is a good start, IMHO.

Greetings, Tom

[maproom]

I wouldn't be worried by lead in glass Go stones.

Lead in paint is a serious problem. Children can eat flakes of it, and can be poisoned as a result. But this happens because flakes of paint are to some extent soluble. But glass is not soluble; not in water, not in stomach acid and other acids, not in alkalies; that is why it is used for glassware. So if a child swallows a glass Go stone, it will just pass through, unaffected.

[Bonobo]

I wouldn't be worried by lead in glass Go stones.

Glass Go stones certainly don’t contain lead.

Lead in paint [..] to some extent soluble. But glass is not soluble [..] So if a child swallows a glass Go stone [..]

Yunzi is NOT glass, it is a ceramic, it is mostly stone powder that has been sintered, i.e. pressed and baked together with great heat, and thus it is porous.

They used to (and some perhaps still do) add lead powder for weight, and this lead can be abrased from the porous surface with skin contact. Also, it has happened that yunzi stones break, and, according to those who wrote about it, some of their broken stones contained a white-ish, powdery substance. I assume this can happen when for example the sintering was incomplete and the stones have not been “baked” long enough or with too little heat.


Greetings, Tom

[xed_over]

I wouldn't be worried by lead in glass Go stones.

Glass Go stones certainly don’t contain lead.

Lead in paint [..] to some extent soluble. But glass is not soluble [..] So if a child swallows a glass Go stone [..]

Yunzi is NOT glass, it is a ceramic, it is mostly stone powder that has been sintered, i.e. pressed and baked together with great heat, and thus it is porous.

They used to (and some perhaps still do) add lead powder for weight, and this lead can be abrased from the porous surface with skin contact. Also, it has happened that yunzi stones break, and, according to those who wrote about it, some of their broken stones contained a white-ish, powdery substance. I assume this can happen when for example the sintering was incomplete and the stones have not been “baked” long enough or with too little heat.


Greetings, Tom

its not added for weight. Its added to lower the melting point for the glass (or ceramic, which is a form of glass), to make the molten glass easier to work with.

viewtopic.php?p=90688#p90688

and the powdery substance inside broken stones is just the "stone" mixture itself from improper cooling.

[Bonobo]

[..]

its not added for weight. Its added to lower the melting point for the glass (or ceramic, which is a form of glass), to make the molten glass easier to work with.

viewtopic.php?p=90688#p90688

and the powdery substance inside broken stones is just the "stone" mixture itself from improper cooling.

Thank you, I’m aware of that thread, yet I’ve read different information about this elsewhere.

OK, so it’s not added for weight, but it has been added. BUT glass ≠ ceramic, glass is rather a subcategory of ceramics, as I understand it.

http://chemed.chem.purdue.edu/genchem/t ... html#glass
http://www.differencebetween.net/object ... -ceramics/
http://en.wikipedia.org/wiki/Ceramic
http://en.wikipedia.org/wiki/Glass

Thanks, I’ve learnt something

Before I only knew that glass is amorphous and made from molten silica, plainly said: molten sand (plus some additions for lowering the melting point), and that ceramics are baken (burnt? kilned? It began with clay), and that they are not molten as much as glass, or better perhaps to say that they are not as liquid/fluid/ as molten glass is. And that Yunzi is a sintered ceramic made from stone meal (with a süper sikrit recipe), under pressure and heat, thus the porosity. I have a set of Yunzi with a green-ish luster which are said to be made with a certain amount of powdered green Jade.

Sadly, I can’t remember all my sources since it’s been a while since I learnt about this, but there’s some info about Yunzi (though not about the lead, unless I overlooked it) on Sensei’s Library here: http://senseis.xmp.net/?Yunzi and http://senseis.xmp.net/?Yunzi%2Fdiscussion

Respectfully, Tom

[xed_over]

Before I only knew that glass is amorphous and made from molten silica, plainly said: molten sand (plus some additions for lowering the melting point), and that ceramics are baken (burnt? kilned? It began with clay), and that they are not molten as much as glass, or better perhaps to say that they are not as liquid/fluid/ as molten glass is. And that Yunzi is a sintered ceramic made from stone meal (with a süper sikrit recipe), under pressure and heat, thus the porosity. I have a set of Yunzi with a green-ish luster which are said to be made with a certain amount of powdered green Jade.

looks pretty molten/liquid/fluid to me...
[youtube]https://www.youtube.com/watch?v=rPdk6PbFbZk[/youtube]