FAQ

Who are you, James Kasper?
What prompted you to undertake this project?
It’s a huge project. Did you do all the work?
Lori Roderick, ceramist, had a personal interest in doing a C04 electric firing in her kiln. And a C04 woodfiring that I did for her. Those are the nice cups. In the belief that her C04 electric fired cups would serve just as well as a set of my bumpy cups, they are included. I did a second set of my cups to go with her clean woodfired cups to allow better comparison to my dirty woodfire cups. 

Shawna Johnson, Maggie Adams, and Lisa Koblenz were hired to do the photography.  If they hadn’t done so, you wouldn’t be able to view these results as I was pretty burned out by then! 
How long did the project take?
What did you hope to achieve with the test?
Why did you pick C04 and C5 firings?
How did you choose the clays and glazes?
Hoping that these tests will inspire others to explore, it seemed best to use readily available materials – hence commercial clays and glazes.

For both C04 and C5 I chose a range of clay colors. There were less to choose from for C04.

Glazes were selected based on my guess as to which might be resistant to woodfire effects, which might be likely to show woodfire effects, and to try some colors that don’t usually work well in C10 woodfirings.
Why commercial clay and glazes? Did you make your own as well?
When Lori Roderick, ceramist, contacted me about doing some research firings I used that as the boot to get me going. If others want to play with these firings it is easier to get started without the need to develop their own clays and glazes. It is quite reasonable to expect that the firing results could be enhanced by formulating one’s own materials.

I have not yet made my own clays and glazes for these temperatures.
How did you make the bumpy cups?
There are two sets of C04 cups that look very different from the bumpy cups. What’s up?
What are ‘real’ pieces? What’s the story about the odd forms?
With a shelf loaded with cups the woodfire flame tends to rise away from the cups towards the rear of the shelf so that the fly ash and flame mostly interact with the firebox side pieces. 

To look at a more realistic shelf loading where the fire and ash can interact with most of the pieces, a variety of shapes with different heights were made – hence ‘real’ pieces. The firebox edge of the shelf was loaded with short pieces. Each row going back had taller pieces and the forms used had a range of shapes to interact with the flame and ash differently.
Do you have all three kiln types?
I have an electric kiln. Until recently I had a woodfired kiln with propane burners to help with preheat. All the woodfirings used this kiln. The burners were not of a size to get the kiln to C10. I was able to gas fire the C04 cups. For the C5 gas firing and the C04 ‘real’ pieces I was able to hire out a gas kiln at Access Arts, Columbia, Missouri. Maggie Adams, one of the clay tech persons at that time, did those firings.
How were the cups glazed and loaded?
The bumpy cups were wadded on the rim and fired upside down roughly .25 inch from the shelf. Half the outside has three brushed coats of glaze, the other half has one coat of brushed glaze. The inside has two brushed coats of glaze. Facing the woodfire flame, half the cup is one glaze coat, the other three glaze coats.

Lori Roderick’s  ‘typical/usual’ cups were fired lip up. There are three coats of brushed glaze on the inside and outside.
What’s the difference between ‘clean’ and ‘dirty’ woodfiring?
In both cases propane was used to preheat the kiln.

During a clean woodfiring the coals are not stirred so only fly ash and flame interact with the cups.

In a dirty firing, coals are stirred up onto cups in addition to the fly ash and flame interaction. This has the most impact on the cups on the front edge of the shelves.

In neither case were the firings held at the desired cone for an extended time.
What are the main take aways?
There are color effects for the glazes in electric firing by simply using darker clays. These results might be of interest to electric firers.

There are differences between gas reduction and woodfiring. Whether there are enough differences and effects for woodfirers to consider loading the tail of the kiln with work that doesn’t need to reach C10 and still looks different than gas fired C5 work, only time will tell.
What are you going to do with all those cups?
Are you planning to do more tests?
Can you test my clay and glaze?
Are you getting support from clay or glaze companies?
What (3) C04 clays were used?
What (29) C04 glazes were used? (Please be sure you want the C04 glazes and not C5 as the codes are reused.)
Spectrum 250 Satin Clear a 

Spectrum 253 Satin Black b 

Spectrum 254 Satin Taupe c 

Spectrum 700 Clear d 

Spectrum 701 Snow White e 

Spectrum 702 Porcelain f 

Spectrum 703 Light Gray g 

Spectrum 704 Charcoal h 

Spectrum 709 Powder Blue i 

Spectrum 714 Sea Spray j 

Spectrum 724 Mango k 

Spectrum 731 Rose l 

Spectrum 734 Butter Yellow m 

Spectrum 749 Christmas Red n 

Spectrum 755 Really Red o 

Spectrum 802 Ivory Speckle p 

Spectrum 805 Spiced Honey q 

Spectrum 907 Autumn Leave r 

Spectrum 921 Iron Earth s 

Spectrum 929 Mocha t 

Spectrum 931 Dove Gray u  

Spectrum 932 Pistachio v 

Spectrum 933 Strawberry w 

Spectrum 939 Chocolate Chip x 

Spectrum 948 Tortilla y 

Spectrum 951 Sunset Red z 

Spectrum 952 Meteor Shower aa 

Spectrum 962 Phoenix Red bb 

No glaze none
What (15) C5 clays were used? 
Aardvark Obsidian D 

Flint Hills Clay Black E 

Flint Hills Clay Buff Plus F 

Flint Hills Clay Porcelain G 

Kansas Clay Red Cobblestone H 

Laguna B-3 Brown WC391 I 

Laguna B-Mix 5 w/grog WC436 J 

Laguna B-Mix Speckled WC408 K 

Laguna Electric Brown WC866 L 

Laguna Frost Porcelain 6 WC437 M 

Laguna SB Red WC394 N 

Standard Clay Brooklyn Red 308 O 

Standard Clay Dark Brown 266 P 

Standard Clay Speckled Clay 760 Q 

Standard Clay White w/molochite 181 R
What (38) C5 glazes were used? (Please be sure you want the C5 glazes and not C04 as the codes are reused.)
Spectrum 1106 Crimson a 

Spectrum 1107 Black b 

Spectrum 1108 Butter Yellow c 

Spectrum 1110 Turquoise d 

Spectrum 1111 Holly Green e 

Spectrum 1113 Texture Milk and Honey f 

Spectrum 1114 Gold Rain g 

Spectrum 1115 Texture Moonscape h 

Spectrum 1118 White i 

Spectrum 1121 Satin White j 

Spectrum 1122 Satin Mottle k 

Spectrum 1123 Satin Speckle l 

Spectrum 1126 Satin Black m 

Spectrum 1127 Satin Turquoise n 

Spectrum 1136 Royal Blue o 

Spectrum 1140 Texture Kiwi Fruit p 

Spectrum 1142 Texture Wheat q 

Spectrum 1145 Texture Autumn r 

Spectrum 1147 Delft Blue s 

Spectrum 1164 Dark Red t 

Spectrum 1165 Bright Red u 

Spectrum 1181 Texture Cloud v 

Spectrum 1182 Texture Jungle w 

Spectrum 1183 Texture Dark Cloud x 

Spectrum 1185 Forest Green y 

Spectrum 1186 Soft Pink z 

Spectrum 1187 Clear Crackle aa 

Spectrum 1193 Fire Engine Red bb 

Spectrum 1197 Reactive Red cc 

Spectrum 1401 Cherry Salmon Shino dd 

Spectrum 1403 Citron Shino ee 

Spectrum 1404 Wasabi Shino ff 

Spectrum 1406 Ahi Shino gg 

Spectrum 1408 Jalapeno hh 

Spectrum 1410 Miso Shino ii 

Spectrum 1411 Nutmeg Shino jj 

Spectrum 1412 Charcoal Shino kk 

No Glaze none
What glazes were used for the C5 Real Piece cups?

Disclaimer: The results should be considered suggestive rather than predictive. You should test in your own kiln for results and suitability for your intended use before going into production. Some firings and atmospheres may be outside the clay and glaze makers suitability for food safety – please visit their websites for information. These tests did not examine for food safety. 