Friday, June 14, 2013

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




18 comments :

  1. WOW I know that took a long time but what a fun experience to share with us. I love the new textures!

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    1. Kristen - I was feeling proud and excited. I hadnt been responsible for loading in years. My colleague is a bit of a control trek, you see. And I have to fight to get my little, easy to spill, hard to load pendants in there... Ok "fight" is maybe a bit strong... you know what I mean.

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  2. That's an awesome kiln. I need to see this bad boy when I get a chance to come and visit.

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  3. Anytime Diana! You know you are welcome. I should show you the raku area. It is also a "diamond in the rough" but it does the job...

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  4. WOW that is very cool, always love seeing the process and I had no idea it was that amazing!!

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    1. It has an air of mystery, Kristi. With the reduction atmosphere you arent guaranteed any certain results as the alchemy/magic happens. There is a Zen to it - as you have to accept the results you are given.

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  5. Love seei g those big brick kilns! Really enjoyed this post!

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    1. Thanks Karen! I didnt want to get too technical - but I wanted to express the reality of a shared studio. Ups and downs...

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  6. What an awesome post-everything I know about ceramics I gain from reading blogs! So cool, and I cannot wait to see your finishhed pieces!

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    1. Me too, Patti! I was there today prepping for Mondays Clay Camp opening day. Its hard to look at said kiln and not be able to open it...

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  7. Woo hoo - that is one big momma with fire in her belly - I had no idea...what an interesting post . Thanks Jeny

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    1. When I do a follow up I will include a pix of a student in the kiln - very Hansel and Gretel... its maybe 4 feet tall inside?

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  8. This was a fascinating read! So this is how the charms were made for the Component of the Month? It really makes me appreciate all the work and skill that goes into them! Thanks for sharing.

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    1. Linda - the CoM charms are "low fire" earthenware. They were made in my home studio and fired there as well. The give away to low fire is brighter colors!

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  9. Very cool post! Loved seeing the kiln and the process. Sounds exhausting! And hot.

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    1. It was hot. And it wasnt a terrible day. Loading in August in the humidity is hellish.

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  10. Wow! That whole shelf-by-shelf process is fascinating ... and an art all its own. I really enjoyed this post and can't wait to see the finished pieces!

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  11. Woo Hoo! It turned out great!!! you can see all the pix on my blog today! http://www.jdaviesreazor.com/blog/clay_camp_and_kiln_unloaded

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