This series of tests was inspired by Tom Jaszczaks workshop at Santa Fe Clay last summer. I had been firing a few select items for the last 3 years in electric kilns to cone 1 or 2 and was curious about how soda firing at this temperature would work out. I already had a clay body that I had tested and used at that temperature and knew it wouldn’t bloat or deform (Laguna R2 or R2 with grog). I had no idea how any of the previous cone 1 tests I developed back in 2012 & 2013 would fare in a reduction soda firing. During the workshop I was able to get a few of the glazes I had previously made tests for into the kiln. Unfortunately my previous glazes either blistered or melon skinned and were not generally happy with the atmosphere. These glazes were predominantly nepheline syenite, generally around 60-70%, and frit. So last fall I sat down and picked a few lowfire glazes out of my recipe lists and began making small test batches. I selected glazes to contrast each other. I selected glazes that were opaque, clear, satin, or gloss, but of more interest to me was the predominant flux of each base. I tried to choose a diverse selection of fluxers. The main categories were: Frit (3110, 3124, 3134, 3195, and combinations of the previous), Lithium, and Gerstley Borate. There were also a few recipes that paired Soda Ash or Borax with other melters but they were never a primary component of the glaze.


I was expecting to see more results that were either melon skinned or blistered. There were really only a few tiles that didn’t look like they should be used in this type of firing. The most notable of these was the Moonalis Chartreuse (which is a nepheline syenite heavy recipe and bubbled and blistered quite baddly) and Sar Guntel Young II (which is 70% Lithium carb and is beautiful but shivered off of the R2 terracotta). There were a few others that blistered and you will see them in the photos I am sharing in this post.

The most surprising thing for me was the number of clear bases which turned red. I am not sure whether they were picking up copper from the atmosphere, iron from the claybody, or a combination of both. When looking at the photos of the tiles you will see a number of base glazes that have a mauve-iron red cloudiness to them. They do not have any colorants in them but in my next cone 3 soda firing, I will test a few of these with colorants to see how much the red coloration changes.


I also selected a variety of slips for this firing and even a few ball clays used on their own. I was curious about a few standard midrange and high fire slip recipes as well. I was pleasantly surprised by a majority of these slips especially the ball clays and high fire slips. All of these slips were applied to bisqued tiles and could stand to be thicker. That is something I will test in future firings.

Overall I am very pleased with the outcome of this firing and with the majority of my tests. Enjoy and feel free to use any of these recipes.

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