Here is what my friend in Japan shared about Ki-Seto glaze that he said I could share. He did not invite direct email communications with you... which is quite a normal response...... and I will not press it. What he gave is a very typical Japanese kind of answer to such overt questions. They have a distinct belief about how one appropriately learns about ceramics (and other crafts). Remember things like 7 year apprenticeships...and stuff like only wedging clay for a year. Things in Japan are not often directly said. So 'read between the lines' here.
"John san Ohayo gozaimasu. John Kizeto glaze is just simple ash-glaze.
The recipe is around "Ash : Feldspar = 50 : 50 .
Slow cooling and lower firing is important to get Kizeto-skin.
Also fine-sandy high refractory white clay is required. That all !
There is nothing any more. I told you the Secret of Kizeto already.
This is my answer. Nobody taught me those. I did not ask to somebody.
I asked only to Old original Kizeto.
Kizeto is the most difficult one, I think. True-Kizeto makers are very few.
I think, true-Kizeto makers got right answer separately by trial and error.
The best way to get good results is only to pile up the experiences.
Old Kizeto taught me only. Inference and observation for original Kizeto is only a way to right answer."
So there you have it straight from a mid-sixty year old potter who makes some of the most literally accurate Ki-Seto glazes I have seen. A lesson in Ki-Seto... and a lesson in learning about ceramics.
Cutting to the chase........ you now have been given the basics you need and the primary source resources........ so get to work .
I'm reminded yet again of the Hamada Shoji quote I have as my tagline on Facebook: "Clay and wheel; they teach us."