Art 399: CUPS 71-80

It might be time to talk a little bit about firing methods.  There are 3 basic ways to fire a piece: Electric kilns (oxygen always present), Gas fired kiln (oxygen is controlled, either reduction or oxidation or even), or an Atmospheric kiln (Soda, Salt, Wood, Raku are all examples of atmospheric firings).  In an atmospheric firing there are many variables... you never know how things are going to react with inside the kiln, and often, that is where the beauty and mystery comes in.


With soda and salt firings it requires a gas kiln that is dedicated to that substance.  Salt firing is a rather toxic process, so USC doesn't allow salt firing on campus.  But we do have a dedicated soda kiln.  So during the semester when someone was firing the soda kiln I randomly included a couple of glazed pieces to see how things come out.


I pulled this off the web about soda firing:  
Soda firing is an atmospheric firing technique where “soda” is introduced into the kiln near top temperature (2350°, ∆10). The soda that we use is: sodium bi-carbonate, also know as baking soda (the Arm and Hammer™kind), and sodium carbonate, which is also known as soda ash.... 
The soda vaporizes and is carried on the flame throughout the kiln. The soda vapors create a glaze when it lands on a piece (or a kiln post, or the wall of the kiln). Wherever the flame travels- so does the soda. When placing the pieces in the kiln during loading, you have to think carefully about when and where you want a piece to get lots of soda, or when and where you want a piece to be more protected.... 
The soda vapors aren’t actually colored, but they are reacting with the alumina, silica and iron in the clay (and slips) to create the various colors of flashing, and associated textures. The resulting colors can be a range of oranges with yellow and red tones, to rich browns, golds and tans. 


Google a couple of images to see the variation that can be achieved.  I really like the variation on raw fired pieces - the oranges and burnt color that is just a reaction with the clay.  So on some of these pieces I just glazed the inside of the cup and the rim.  But the oranges didn't  happen with the clay I was using (the porcelain and porcelaneous stoneware).  Not enough iron in the clay I think?  Anyway, review my experimentation.

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Resist Etching.  Ocean Green and Basic Green Celadon.  Fired first in Electric Kiln to cone 6.  Then fired Reduction gas kiln, but interrupted at cone 3.  

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Resist Etching.  Ocean Green and Basic Green Celadon.  Fired first in Electric Kiln to cone 6.  

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Photocopy transfer on bisqueware.  Pete Pinelle's Clear glaze (inside and rim).  Soda fired 4.16.10.  Glaze did not mature, soda fired again 5.1.10.

A photo transfer is a way of transferring a photocopied image onto a piece of greenware or bisqueware.  The photocopy process must be on a carbon-based printer, and the process is interrupted before the heat process, so the image is a powder.  Once you have the image it is a simple process of rubbing the image onto the piece.  Use a fixative to make sure it stays in place.  These were my first attempts, again, not knowing how they were going to come out, and I didn't glaze over the transfer image, afraid it would run off.  I thought the soda would be the best way of sealing the image, just using the soda as a glaze.

Also, Cups 73, 75, and 76 all looked like cup 74.  Tall, nuclear cone shape, with really nice handles.  A nice set of 4.  But the handles dried at a different rate than the cup, so all the handles broke.  !!!  Another lesson on drying rates and construction.  So I trimmed off the cracked rims and handles and used them as test pieces.

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Acero glaze (inside and rim).  Soda fired 4.16.10.  Glaze did not mature, soda fired again 5.1.10.

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Photocopy transfer on bisqueware.  Temple White glaze (inside and rim).  Soda fired 4.16.10.  Glaze did not mature, soda fired again 5.1.10.  Photocopied image was completely lost in the second firing.  Dang!

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Photocopy transfer on bisqueware.  Temple White glaze (inside and rim).  Soda fired 4.16.10.  Glaze did not mature, soda fired again 5.1.10.  Again, image lost in second firing.

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Photocopy transfer on greenware.  Tomato Red (inside and rim).  Soda fired 4.29.10. 

On these pieces I used wax over the image to hold it in place... but instead I think the image just melted off with the wax!  Dang again!  I was really excited about these.... I really need to lower my expectations.

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Photocopy transfer on greenware.  Cannon Ball Bllue (inside and rim).  Soda fired 4.29.10. 

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Photocopy transfer on greenware.  Chun Clear (inside).  Soda fired 4.29.10.  Again, this is where I discovered that the Soda kiln goes into reduction... instead of blue I got pink.

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Photocopy transfer on greenware.  Choy Blue (inside and rim).  Soda fired 4.29.10.  Wax melted off the image.  So disappointing.