Lead check for Yunzi stones

A Lead Check kit from Home Depot for about $6.

I was recently alerted by a reader about the surface-accessible lead content (chemical symbol = Pb) of his Yunzi stones that he had purchased in October of 2007 from Yellow Mountain Imports. All the hullabaloo about lead in children's toys from China piqued his curiousity so he initially tested his stones with a kit similar to the one pictured above. The test came out positive.

The old recipe for Yunzi included lead oxide which helped reduce the brittleness of the white stones but current formulas are no longer supposed to use this.

My reader had access to x-ray fluorescence testing to confirm the kit results. The white stones contain almost 200 times the amount of lead allowed by US law in paint, and the black stones about 5 times.

My Own Test

I picked-up a Lead Check kit from the local Home Depot to do my own test. As some of you might recall, I had purchased my set in late 2005.


Sadly, the results were positive and showed that my stones did have surface-accessible lead.


Here's a close-up of the test-swab which turned pinkish-red after being rubbed on a white Yunzi stone for less than thirty seconds.


Educating yourself on the risks of lead

The risks from dermal contact (through the skin) are low. Children under the age of six are the most vulnerable to lead exposure because their bodies and nervous systems are still developing rapidly and because they are most likely to place objects in their mouths (thus maximizing exposure).

To better understand the risks and concerns of lead, please see the following links:

• Heavy Metal: How dangerous is lead (Slate Magazine, Eliza McCarthy)
• Guidance for Lead in Consumer Products (US Consumer Product Safety Commission)

YMI responds to take care of its customers

The reader and I had corresponded with YMI regarding these findings. YMI was caught off-guard as they had received assurances from the Yunnan Weiqi Company (YWC) that their shipments of Yunzi were lead-free. The images below are from documentation provided in 2006 certifying that the stones had no lead content.

Certification from the Yunnan Weiqi Factory showing zero lead content.

Test results from the Yunnan Weiqi Factory

YMI conducted its own tests and found surface-accessible lead on samples of their Yunzi.

YMI brought this matter up with the Yunnan Weiqi Company. The YWC received two new official lab results of the most recently produced Yunzi, confirming 0.19% lead in the white stones and 0% in the black. They were rather baffled because they had taken lead out of the formulation in early 2006. The lead had occurred somewhere in their supply chain and they eventually narrowed it down to their zinc supplier. The zinc supplied for use in the Yunzi contained lead. The YWC will be switching zinc suppliers and will also try making Yunzi without zinc.

In the meantime, YMI is working to put together an exchange program for their customers who have concerns about surface-accessible lead. Obviously, because the YWC is still sorting-out its sourcing, it may take as long as a month before YMI has lead-free Yunzi available. Pong Yen at YMI has advised that if anybody is immediately concerned and does not want to wait until then, they can send in their set of Yunzi stones (without their bowls) and YMI will send them a set of marble stones as a replacement.

A complete set of stones and shipping address should be sent to:

Yellow Mountain Imports
Yunzi for Marble Exchange
227 S. Raymond Ave.
Alhambra, CA 91801

You can also contact them via their website.

ADDENDUM (Jan 3, 2008):
Yunzi stones from the Yunnan Weiqi Company are sold all around the world by many vendors. If you did not acquire your stones from Yellow Mountain Imports and have concerns about the stones' lead content, please contact the vendor who sold you your set. Regretfully, other vendors may have their own policies with regards to safety-issue exchanges.

A discussion on this matter is also active on GoDiscussions.com. Click here to go directly to that topic.