Feel the heat! Ceramic cone 10 reduction firing...

This was on my plate this week - literally. It is a plate full of porcelain charms and pendants stamped with new (to me) designs and textures. Do you recall the post a while back where I made molds from a plethora of organic items? Star Anise, coral, sea urchins... they are finally seeing the inside of the kiln! 

The process can be slow - create, dry, refine, fire, glaze, fire... depending on the creator this can be a week - or a few months! For me I work in 2 very different clay categories. I work in earthenware, a lower temperature clay for my sculptural "Mythic Nature" pendants. I use commercial low fire glazes as they afford me a colorful, reliable palette with which to paint. These pieces fire in my kiln at home, an electric kiln, whenever I feel the need. Easy peasy. ( Temperature range - ballpark 1900F)

I also work at a ceramics studio where we fire to cone 10 reduction. ( More on reduction in a sec, hang on...) There are stoneware clays in a variety of colors and porcelain. The firing is done in a large, hand built gas kiln out in the courtyard. Its a bit rough, but a work horse. But it might get fired once a week, and it is a group firing overseen by my colleague who teaches the adult class. She fits in what she can, theoretically including student work before instructors, and trying to get a few pieces in from each student. So there is the waiting game, and I am an instructor so... Sigh. It can take a while to get small fiddly little charms in the kiln. 

Big Bertha in reduction. Yes - flames are flitting out!

With Beadfest coming in a few months - its a rush to make hi fire things now! I hope to include a few in each firing this summer, but classes are smaller and the kiln fires maybe every other week. 

This week - my colleague was away. So I loaded the kiln, and  it fired  today. And we did make sure to get my half shelf of charms in.... I wanted to show you the process: 

My porcelain

From the last firing... 

The kiln on the far left. Panarama shot. Pots everywhere... we got 95% of this in the firing. 

Building shelf by shelf, the full kiln, bricking up the doorway.

It took the 2 of us two hours. While this style kiln allows great flexibility for placement of shelves, it has to be rebuilt and reconfigured every firing. It fires with propane to app. 2377 degrees, and can take approximately 8-10 hours. It will cool for a full day, and as the weekend is here - we wont unload until Monday. It is nervous anticipation, like taking an exam and awaiting Christmas morning - all in one!

The reduction firing - in layman's terms - means that during the firing cycle one purposefully reduces the oxygen intake via vents on the kiln. This causes a "reduction" atmosphere inside the kiln - oxygen is leached from the clay and the glazes - magic! Or to be technical: "A reducing atmosphere is also used in order to produce specific effects on ceramic wares being fired. A reduction atmosphere is produced in a fuel fired kiln by reducing the draft and depriving the kiln of oxygen. This reduced level of oxygen causes incomplete combustion of the fuel and raises the level of carbon inside the kiln. At high temperatures the carbon will bond with and remove the oxygen in the metal oxides used as colorants in the glazes. This loss of oxygen results in a change in the color of the glazes because it allows the metals in the glaze to be seen in an unoxidized form. A reduction atmosphere can also affect the color of the clay body. If iron is present in the clay body, as it is in most stoneware, then it will be affected by the reduction atmosphere as well."

So there.

Its art and alchemy. 

Its primal. 

Its hot. 

Its chemistry. 

It can be a surprise... 

And I have to wait until Monday... 

Have a good weekend!

Jenny 

www.jdaviesreazor.com