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Constructing The Pit

The pit is dug to provide wind protection and to retain heat sufficient to permit the fuming process. The pit may be circular or trench like. When firing by myself or with one other person at the beach, I use a perforated oil drum or the fire pit rings provided by the State. When firing in a group, I dig a trench large enough to hold all the pots. The following tables describe two very different layering techniques in the construction of these pits. (Note: any combination and layering that suits the potter can be used. There are no rules, only guidelines.)
Table I Small Pit in a Fire Ring or Perforated Oil Drum - For 1-2 potters
LayerCombustibles and ChemicalsThickness in inches
 13Cow pies surround the entire mound from the ground up 4
 12Top layer is composed of leaves, twigs, and weeds 6
 11Top dry seaweed layer 6
 10Pots intermingled with kelp, sea grasses, small driftwood 4-16
  9Seaweed and Magic Dust layer 2
  8 Leaves, twigs, and weed layer  5-10
  7Pots intermingled with kelp, sea grasses, small driftwood 4-16
  6Seaweed and Magic Dust layer 6
  5Driftwood, ground level 4
  4Seaweed roots and Magic Dust layer 6
  3Cow pies or damp seaweed to tamp the fire  6
  2Coal bed 3
  1Bottom layer of pit is clear of rocks or glass 
Why do we use these combustibles?

1.

Vegetation from the sea is impregnated with sea salts containing many trace elements that give unique coloration to the ware. As an alternative you can soak other combustibles in table or sea salt and dry prior to pit firing.

2.

Cow pies serve three functions: When dry, they easily burn to earthenware temperatures. They impart various colors on their own when they burn: blacks, greens, grays, browns. They cover the ware with a clinging yet easily removable ash. This ash blanket promotes a local reduction atmosphere necessary for copper reds.

3.

“Magic Dust” is a term I coined to describe a mixture of one third copper carbonate and two thirds table salt that is used to “enrich” the pit fuming atmosphere. Magic Dust is sprinkled on combustibles but not directly on the ware. Salt will adhere to the clay and eventually “eat” right through it. Care must also be taken with seaweed pods as they contain a high concentration of salt that will transfer to the pot.
  N.B. Warning: Wear a mask, protective goggles, long sleeves and pants when sprinkling Magic Dust. Copper is a respiratory tract irritant. Repeated inhalation of dust can cause sinus congestion, ulceration, and perforation of the nasal septum. Contact with eyes can cause conjunctivitis, discoloration, and ulcers on the cornea. It can also irritate and discolor the skin. Wash immediately.
The pit is dug 14-20 inches deep into the ground, care being taken to remove all rocks and glass fragments. Coals are laid in the bed, lit and allowed to reach a glowing stage. Damp seaweed or dry cow pies are placed on the coals to tamp the flames. This layer takes several minutes to ignite giving you time to construct the rest of the pit which can be 3-5 feet above the ground. The pit will burn actively for an hour or so. Because of the liberal use of cow pies, be aware that this pit creates a lot of smoke for 15-25 minutes. Do not disturb the ash layer covering the pots when you are trying to promote local reduction for copper reds. This pit construction permits pockets of reduction within an overall oxidizing atmosphere. Some of the colors obtainable are listed in Table II. When the pit reaches about 1100˚F green copper fumes will be easily seen rising from the flames. Warning: Do not inhale this smoke. Salt becomes active around 1400˚F. Colors will swirl within the pit and chlorine vapor will be visible.  Do not inhale the smoke.  The pit will have an orange glow and will easily reach 1860˚F. When the pit cools to about 500˚F, you can elect to cover it with steel sheets to protect the ware from the wind and yet not influence the fumed colors. (How do you know when the pit is 500˚F? Gain “tactile sense” by placing your hand near an opened kitchen oven heated to that temperature.) The pit is not disturbed and allowed to cool naturally to the point where pots can comfortably be handled.

This one person small pit construction is used to maximize the natural and stunning sea salt effects from fuming. Many colors are possible as well as impressions of the sea plants.  Fuming chemicals are used to enhance color development.
 

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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.

             
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