| Table II Color Palette Chart |
| Combustibles and Chemicals | Expected coloration on cone 018-014 bisque | | Hardwood sawdust | Black, dark gray | | Hardwood coals | Black, smoky gray, blue-grays | | Cow pies from grass fed cows | Gun metal black, jet black, golden yellows | | Cow pies from grain fed cows | Dark greens, grays, blacks, browns | | Driftwood | Blue-grays, aqua shades, gray-blacks | | Seaweed roots | Browns, rust, honey | | Kelp leaves | Yellow, orange, peach | | Kelp pods | Orange, brown | | Saline grown leaves, twigs, grass | Golden yellows, greens | | Table salt | Orange, yellows | | Sea salt | Salmon, orange, yellow, gold, peach | | Copper carbonate | Green, black, maroon, reds | | Cobalt carbonate | Blues | | Ferric chloride | Iron reds, yellows, oranges |
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| Further precautions: |
1. | Ferric chloride solution (concentrated or diluted) can be sprayed or brushed directly onto the ware before placing in the pit. Ferric chloride is caustic. Do not breath it, do not get in on your skin or in eyes, do not swallow it. |
2. | Cobalt carbonate (less than 0.5%) solution can be sprayed or brushed onto the piece before it is bisqued or on the inside walls of saggars. Cobalt is a mild skin, eye, and respiratory irritant. It can cause skin allergic reaction. Inhalation can cause asthma like symptoms, lung damage, and pneumonia. Absorption causes vomiting, diarrhea and “hot flashes.” |
| Pre-heating can be done in three ways for this small pit: |
1. | Place pots around the pit rim while the coal bed matures. Turn the pots every few minutes to ensure even heating as you move them gradually towards the hot coals. |
2. | Place pots in a portable barbeque with heated charcoals or low propane flame and heat to about 300˚F. |
3. | Place pots in pit with an extra thick layer of tamping materials so the pots will be in a steaming atmosphere before the combustibles fully ignite. |
4. | The trench style of pit fire does not require preheating as the pots are in a natural draft that gradually heats them from the top or one side. |
| Table III Trench Style Pit Fire Used For Groups With Many Pots |
| Layer | Combustibles and Chemicals | Thickness in inches | | 8 | Leaves, twigs, kindling | 6 | | 7 | Hardwood planks or small firewood pieces | 12 | | 6 | Small intertwined branches | 24 | | 5 | Cow pies | 4-6 | | 4 | Pots interspersed with small twigs or driftwood | 10-20 | | 3 | Magic Dust, minimum one cup per square yard | liberal | | 2 | Hardwood sawdust | 8 | | 1 | Bottom layer of pit is clear of rocks or glass | |
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| This trench can be deep or shallow. (The largest I have used was 6 feet deep by 25 feet long by 7 feet wide.) If a shallow pit is desired, hardwood pieces or split logs of firewood are placed vertically along the sides of the pit to “extend” the trench walls from the ground up. This pit is lit at the top when the trench is deeper than 2 ½ feet. If the trench is shallow construct it so that the wind will blow from end to end and then light it from the end receiving the wind. When that windward end burns, it will enable pre-heating of the ware to take place as the fire follows the draft. I do not place pots that I want preheated too close to the lit end of the shallow trench. Stand back and watch the fire roar. The same colors, temperatures, and precautions that were described for the one person pit apply. |
Post Firing |
| | 1. | Remove the ash from the interior of the pots. |
| | 2. | Do not wash the pots. You do not want salt deposited on the surface to permeate the body of the piece. Pit fired pots are decorative, not functional. |
| | 3. | Carefully shake off or wipe any ash residue adhering to the surface. Single edge razor blades or credit cards are useful tools in removing carbon or wire fragments that stick to the pot. Be careful not to scratch the delicate surface. |
| | 4. | The pit site should be cleaned and left as natural as you found it. Remember ashes are very caustic. Wear a mask. |
| | 5. | Pots need to be treated to prevent or retard absorption of water from the atmosphere. The salt in the pit fired clay will react with water vapor and corrode the surface of the pot. For treatment of burnished or terra sigillata pots I like to apply two layers of Johnson’s or Butcher’s Floor Paste Wax for a semi-gloss sheen. Use a soft shoe brush or cotton cloth to bring out the shine. When first applied, the wax will seem to streak and discolor the surface. This will vanish in a few hours. The wax odor will persist for about a week. If a more reflective surface is desired, I use Future Acrylic Floor Finish diluted with water to a 25% acrylic solution. I also use Future, Watco Clear Liquid Wood Wax, or Jasco Silicon Grout Sealer on rough or unpolished textured surfaces. |
Pit firing requires a lot of effort. It is not without hazards: physical, chemical, and toxicological. Yet, when properly done, it is fun and very rewarding. There is fulfillment when fateful chance weaves its magic through the pit’s flames producing unique (one of a kind) ware.
Should you have any questions about preparing your work for an upcoming pit fire event, please feel free to write to me at EduardoLazoMFA@aol.com. |
| Eduardo Lazo is a ceramicist, teacher, author, and consultant. He has been a studio artist for 20 years and lives in Belmont, California. His current ceramic interests lie in two forms of vapor glazed ceramics - Pit Fire (low fire salt) and Kosai Ware (precious metal fuming). Eduardo has an MFA from California State University Los Angeles. Contact via www.EduardoLazo.com. |
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| Reproductions of this article are prohibited without expressed written permission from Eduardo Lazo. © Copyright 2003 Eduardo Lazo. All rights reserved worldwide. |
