"The main question today is: although we can make ash glazes without an excessive amount of effort, can we make ash glazed ware which is distinctive and also appropriate for both us and our times?" Robert Tichane from his book; ASH GLAZES
My exposure to working with ash glazes and ash in glazes goes way back to the very beginning of my making pots. Collecting up various recipes along the way from Warren MacKenzie, Randy Johnston, Marie Woo, Kirk Mangus and many others, the real issue is what is the appropriate pot to use an ash glaze on. Not unlike copper red, determining where to use an ash glaze happens over time through trial and error of form, style and decoration. In time, a judicious use of an ash glaze is just as important as any other surface a potter can use. Ash glazes are not the answer to any and all pots.
Having moved away from strictly ash centered glazes, I have developed a palette of glazes that I have introduced ash to as a smaller percentage of the formula. With the use of ash in existing glazes, most recently, I have been able to come up with Ki-Seto, Karatsu and Tamba style effects. Given the sucess, now when testing glazes, I invariable make up the same formula with additions of 5% to 20% ash just to gauge the results and see what might occur. Some come out rather interesting, others not so much, but they is why it is called testing. The real plus to the ash addition is the runny factor, which I like very much. By putting an "ashed" glaze over a nice stiff glaze, I am able to get some significant amount of running, especially on more vertical forms. There is a very comforting connection from my beginning in pottery as well as the numerous stops along the way, that links up with how I work today when I use ash, right out of the fire(place).
The illustration is of a stoneware mizusashi that was first glazed in a very thin ash glaze with .2% cobalt carbonate. Once mostly dry, I redipped it in a straight ash glaze to promote the running and mottling effects.