Muckin' Big firings!

Twice a year, we get to use the BIG kilns - the outdoor wood-firing and the salt-fired kiln. Both firing types were common in Medieval Europe, so naturally I've been spending all semester getting ready.

The interior of the salt kiln. No, the bricks aren't glazed;
they've soaked up years of salt. So, yes - technically, they're
glazed. 

Both of these are "vapor-firing" methods, in which the atmosphere of the kiln provides some of the chemistry for creating the pottery's surface. In the salt kiln, large quantities of plain table salt are dumped into the kiln during peak heating. Salt is a "flux" - that is, it lowers the melting temperatures of other materials in the kiln, including the silica that is native to every clay body. Wood ash (in the wood-fired kiln) also works the same way, although the chemical composition of salt and wood ash differ dramatically; salt is in the class of fluxes as soda/soda spar, and wood ash is potash/lye.

The flux plus the silica creates glass which forms on the surface of the pot - in other words, a glaze. Potters typically use a suspension of chemicals (silica, alumina and oxides) applied to the clay to create the glaze, but in this case, we are using the atmosphere of the kiln to (at least in part) do the job. 

My goal was to use both applied glazes and "bare" clay for my pieces. I'm using Laguna WC 899 Cone 10 B Mix for wood/salt firings, which is formulated to suck up those fluxes and provide nice effects in vapor-firings. The 5 pieces of 14th century pottery have salt glazes (that is to say, they are formulated to look like salt effects without the salt atmosphere) applied to the interiors of the pottery. This leaves the exterior clay raw, which is where the salt should provide a nice matte surface. I also placed 5 tea bowls into the wood kiln; they are glazed with traditional Japanese "shino" glazes, with a dry foot. Shinos are dramatic glazes that have variegated effects. Both types of glazes are said to perform well in vapor firings. 

We'll know on Tuesday.

So, some pictures: 

The salt firing wares. The three bowls on the lower left are mine. 

And the wood. 

Front are two of my tea bowls, staged for the wood kiln. A yunomi is on the left and a rustic winter chawan on the left. 

Another view of the winter chawan. It has an applied slip exterior and then the shino over that. The foot is roughly carved. The pot on the right is my less rustic winter chawan. I have some really high hopes for these chawan.  

The salt kiln loaded and about ready to have the door stacked.