Tuesday, August 19, 2014

Earthenware Experiment- What Went in the Kiln

As I mentioned in one of my earlier sporadic blog posts, I have been playing with earthenware in the studio lately. It's been something in the back of my mind for years to try earthenware in a wood kiln. This is mostly because through my kiln furniture research I knew that many early stoneware potters were also making earthenware, but all in the same kiln. So, the biggest quandary I had was what would earthenware look like in a salt kiln environment?

After spending a day cleaning the kiln and shelves last week, the kiln got loaded up last Friday and the fires started on Sunday.

I used the marbled technique that I recently made a post about both on lids and on the sides of some mugs. All of the pots in the photos to come have been bisque-fired, so these are not the finished products.

I ended up having an issue with a white slip that I tested. It may have been a reaction to the clay I was using at the time of the slip tests (Highwater Lyman Red), but either way, I ditched it because I could not keep it from cracking and flaking. I did fired several bowls that had cracking just to see if the flux (3134 Frit) in the slip would heal with a glaze in the kiln. We shall see.

I switched to a very basic white slip and started using Highwater's Earthen Red clay, which I thoroughly enjoyed throwing with. I kid you not, it's like chocolate pudding between your fingers. The switch proved worthwhile and I had a smooth slip that dried well and played nicely even after the bisque firing.
I am testing several clear glaze recipes. One recipe uses mostly white clays as its base, so it turns a very white color after glazing. The other is basically 3134 Frit and Redart, making for a brown-looking glaze.

I played around a little bit with some manganese, by sifting some raw manganese on top of the glazed surface, and sponging it after mixing it with a white slip. The mugs above have lines of sponged manganese and green slip. I anticipate a deep purplish brown/black, but will wait to see what actually turns out.

Other decorated wares included a few squared bottles and some slip trailed and marbled dishes. I was really excited to see how those turned out in the bisque kiln, and am hopeful for their survival in the firing.

You might think I sound a little pessimistic about how this all might turn out. I'm not pessimistic as much as I am hesitant. There's not really a lot of people wood-firing earthenware here in the states and I think it has a lot to do with our restrictions on lead usage. Lead and lead variants like galena are very forgiving in their fluxing and melting temperatures. They don't craze a bunch, or have major reactions like pitting, flaking, or pin-holing. Those things are what I have heard can happen with earthenware in a wood kiln, particularly if it reduces. As one potters once told me, "it's hard to keep a wood kiln out of reduction" and my kiln has that very issue. We didn't seem to have a lot of reduction during the firing this go-around, but will not really know until we open it up.

So, fingers crossed, I teamed up with Anne Partna from Blue Hen Pottery and together we made enough pieces to fill the kiln. Here are some photos of the stacks in the kiln:

I did an overnight gas preheat, which I have found heats the kiln up to around 225 (F), dries out the interior, and starts to heat the brick up. Heating the brick up seems to be what takes the longest with this kiln because I used all hard brick. The more the brick is heated up, the faster the kiln will roll to the end. The firing proved to be a little lengthier than we were anticipating, but it was still not as grueling as a stoneware firing. We are unloading later this afternoon, so stay tuned!

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