Cone 6 ash glaze tests

I've been meaning to start a blog where I can record my work for a long time. So ... here it is. I work at cone 6 in oxidation. You can see the web page that I keep with my wife at www.m2crafts.ca. She is a soap maker and I am a potter. On this blog I plan to record more of the behind the scenes goings on in my studio.

I've recently been doing some tests to develop a cone 6 ash glaze so I though that this would be a good time to start the blog. The base glaze "Frasca Ash" that I have started with is due to Harry Spring. The PMI article is available online.. I had tried this glaze before with moderate success among a larger group of tests, so this time around I will concentrate on it alone. Here's the recipe in case that link goes down:

   56% Unwashed ash
   11% Calcium carbonate
   11% Custer feldspar
   11% Silica
   11% Ball clay

Harry adds 2% cobalt carbonate or 4% copper carbonate for blue and green respectively.

The ash I'm using is sourced from my charcoal grill. Mostly. I have gotten some from my parents fireplace too. To prepare the ash I seive twice, once through a very coarse strainer and a second time through an 80 mesh chinois. The chinois makes it much easier to get the ash through as you can be much more vigourous about it without worrying about spilling.

For the first test I did three batches. I tried this recipe with plus or minus 5% ash. I used the blue variant for colour. The one on the left is with -5% and the one on the right is +5%. I much prefer the middle one, which is the recipe as it is. The ash glaze is dipped over Bone by Roy & Hesselberth. But this is Bone that has been in a bucket for my production year, so it's changed slightly due to solubles and contamination it doesn't normally look that yellow.

I don't really like the look of the glaze quite frankly. I think it's too bluntly blue. Some of the rivulets are nice, but lack that really authentic ashiness. Regarding the former criticism I'm going to try the baze glaze with some colourants as for other glazes that I like. And the latter problem ... I have no idea how to make it more authentically ashy. I will probably test with a different base glaze to try to solve that.