Last week-end I fired my 12th glaze firing. I had a bunch of experiments going on. First, I mixed up a few blue tests. Blue is a popular color in the gallery and I’m not 100% happy with those I have. I have one blue glaze that works great in combination with others (Bright Sky Blue) but I am still searching for that great stand alone blue. Some folks are big on doing line blends to find new killer glazes. Me? Not so much. I added a bunch of colorants to two different glaze bases I’ve been using and here’s what I ended up with (all tests and work on Axner Axner Maccabee 5):

Left:  MC6 Raspberry base + 0.2% Chrome Oxide+3.8% Tin Oxide+1.1% Cobalt Carbonate+0.5% Copper Carbonate
Right: MC6 High Calcium Semi-Matte Base 2 + 0.2% Chrome Oxide+3.8% Tin Oxide+1.1% Cobalt Carbonate+0.5% Copper Carbonate

The glaze on the right (I’m calling it “Blue Jeans”) looks interesting and is a nice enough color but so far doesn’t do anything magical. Maybe it just needs some rutile… The glaze on the left is nice but is too similar to my Jeannie’s Purple without enough “value add”. Two more glaze tests are going into my next kiln…

I also messed around the with my semi-matte blue (which was a bit too weak). Amazing the difference an extra 0.5% of cobalt and copper carbonate will make…

Left: MC6 High Calcium Semi Matte Base 2 + 0.5% Cobalt Carbonate + 0.5% Copper Carbonate
Right: MC6 High Calcium Semi Matte Base 2 + 1% Cobalt Carbonate + 1% Copper Carbonate

Finally, but importantly, I decided to experiment a bit with my final ‘slow cool’ temperature. In all my previous firings, I followed the ‘Mastering Cone 6” schedule, slow cooling down to 1400 degrees. Those who have read the book very carefully know that there is some ambiguity as to whether the cool to 1400 is essential or whether 1500 will suffice. For those non-potter readers, the sole purpose of a slow cool down is to get interesting glaze effects so it is a personal choice, not a necessity of the craft (indeed, some potters don’t even mess around with a slow cool; once the kiln reaches peak temperature, it is allowed to cool down naturally).

How does one know how low to go? Well, like everything else it seems, one has to experiment with the firing schedule to see what changing the cooling ramp will do to the glazes. In terms of practicalities, firing down to 1500 instead of 1400 means an hour less of firing which in the long run saves kiln element life (and a few pennies) and in the short run means one less hour of me fretting around the kiln. 🙂

Well, happily the shorter cool-cycle worked just fine (great even). There were no visible differences in my key glazes. The glazes that thrive on slow cooling (semi-mattes such as Raw Sienna) looked amazing as per usual and the variegated glazes had lovely crystals. If anything, my Bright Sky Blue looked better and more vivid. Result! If my next firing is as good as this one, I’ll be a happy camper.

Here are a few favorite pieces from the firing:

Set of 2 bowls:  Bright Sky Blue over Licorice Black

Bowl:  Licorice Black, Raw Sienna and Variegated Blue

Mugs:  Bright Sky Blue and Licorice Black