Question on stockpiled clay

[chaeric]

Thanks for the great info!

Regarding point two, someone had told me all modern yixing clay has additives, but I don't think that's true, correct?

You are welcome! Correct, not all modern Yixing has additives. But the vast majority does, and I would have a very hard time believing that a clay does not have additives unless it has been tested. Because I know of cases of people being told that the clay did not have additives, who then got it tested and found out that it did.

Ah, I found where I had read it (from another forum when I was looking up info on the subject).

"So the big turn around happened in 1980. Clay made before this time period was processed without the addition of BaCO3.

Stored clay experiences efflorescence which is when the salt content is expelled from a porous material and sits on the surface. Yixing clay has to be aged and without chemical additives will develop a salty crust. This doesn’t hurt anything it just has to be removed and worked before you can use it.

Barium carbonate prevents this and was solidified as an additive in processing in the 1980s. However many have said it compromises clay quality. (This is also just one of a couple modern accepted additives)

Yixing has not been “pure” since 1980. That’s why the early factory one stuff is so highly regarded.

How it effects it? Not really sure it’s all anecdotal . But the government is the only entity allowed to mine and process the ore, so once they switched production method in the 80s the clay is undoubtably different."

So I take it that the person who wrote this is mostly correct for the mass produced stuff but probably not for vendors who care (such as yourself) or handmade articles then?

[steanze]

"So the big turn around happened in 1980. Clay made before this time period was processed without the addition of BaCO3.

Stored clay experiences efflorescence which is when the salt content is expelled from a porous material and sits on the surface. Yixing clay has to be aged and without chemical additives will develop a salty crust. This doesn’t hurt anything it just has to be removed and worked before you can use it.

Barium carbonate prevents this and was solidified as an additive in processing in the 1980s. However many have said it compromises clay quality. (This is also just one of a couple modern accepted additives)

Yixing has not been “pure” since 1980. That’s why the early factory one stuff is so highly regarded.

How it effects it? Not really sure it’s all anecdotal . But the government is the only entity allowed to mine and process the ore, so once they switched production method in the 80s the clay is undoubtably different."

So I take it that the person who wrote this is mostly correct for the mass produced stuff but probably not for vendors who care (such as yourself) or handmade articles then?

Yes, the post is mostly correct. Most handmade articles use barium too actually, so buying a handmade pot does not mean that the clay is free of additives. There are very very few vendors offering clay tested for the absence of additives so the poster can't really be blamed for not mentioning it... as mentioned earlier, if it's not tested, I'd take claims with a grain of salt, because we have seen cases in which craftsmen claimed that clay was additive free but testing revealed that it wasn't the case.

[Thundercleese]

Taking a break from lurking to say thanks to you all for the great info in this thread.