In 60s and 70s, basically there is only Yixing Factory 1 (Factory 2 initiated in 1980) and no any individual pot artist, it is easy to understand the clay of that era. But in the market, some vendors always like to confuse us, try to make the fakes as authentic.
1.The clay of 1960s and 70s was well refined and without too much impurity. So it is difficult to find too much shiny "mica chip" on the body of 60s and 70s' teapot. (Not the yellow spot, it's normal. The mica chip should looks like a small shiny metal chip.) On the contrast, the clay quality of non-F1 was not as good as F1, so we can find the mica chip occasionally.
2.The clay of 60s and 70s is difficult to find the "black spot" too. Many vendors used to explain these black spots are "glaze spot" of dragon kiln. But the teapots were put inside a "protection case"(匣缽) when firing, how the glaze of kiln can spray on it ? If those spots were cause by firing, it should only appeared on the surface of teapot, why it appeared on both the outside and inside of teapot ? Actually the F1 used downdraft kiln instead of dragon kiln after 60s, where was the glaze spot come from? In fact, it is not glaze spot, it is the "impurity material" of the clay. Most of it were relative materials of iron oxide, it melted out when the firing temperature was high enough. One of the import works when refining the clay is purify. In early period, they used "physical methodology", including use magnet to clean the iron relative materials. It is a time-consumming and difficult job. The F1 did a very good job about this in 60s and 70s, so we almost can NOT find these black spots with naked eye. If you found a lot of these black spots on the teapot, you should be carefully. Until the green label era (late 70s), because the need of high production volume, the requirement of clay was reduced, the clay refining is rough. So the black spots became more common in green label era.
3.Do we need a magnifier to identify the clay of 60s and 70s? The answer is "no". Because the clay of 60s and 70s were very average, we can not see any special feature. We only have to make sure is there any "mica chip" or "black spot" with naked eye. That's enough. The magnifier was only used to see the bottom seal, not the clay.
Totally, if the vendors said the 60s and 70s F1 teapot must with "mica chip" or "black spot", that should be wrong! You should pick the one without it. But after 80s, the clay of F1 has some mica chip and black spot is true. Because the refining work is not as good as 70s. But it should not be too much, if it has too much mica ship and black spot, you still have to consider it was not F1 teapot.
p.s. :The clay with chemical additions has NO mica chip and black spot too. So we should NOT use "with/without mica chip or black spot" as the ONLY criteria to identify the F1 teapot. It's easy to make mistake.
How to identify the clay of 60s and 70s ?
Thank you very much!Chi-Lin Lu wrote: ↑Wed Jan 10, 2018 9:06 amIn 60s and 70s, basically there is only Yixing Factory 1 (Factory 2 initiated in 1980) and no any individual pot artist, it is easy to understand the clay of that era. But in the market, some vendors always like to confuse us, try to make the fakes as authentic.
I really hope you will find the time to share your knowledge with us and post here more!