Controlled Reduced Cooling 4

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Putting various ex-anagama pots through the gas refiring process we looked for perceived improvements and were immediately encouraged by the fact that on this pot a heavy deposit of glaze from Forest Red Gum, originally yellowish brown in the image on the left,  was transformed by the refiring into black, as shown in the image on the right. Other changes on the pot were less dramatic, but also to our liking.

As expected from previous refirings the reds associated with shino glazes were intensified by the gas refiring process. This potentially red glaze, an iron red produced by  using an iron rich glaze in a shino recipe,  substantially off the pace as it came out of the anagama (left) was greatly improved to our eyes (right). The ash glaze on top of it was presumably from Blackwood as this time it became yellowish in the refiring, rather than black  as in the image above.

One of the reasons we chose to use Blackwood as a fuel is that where the resulting ash glaze was thin it produced a red blush, and as it thickened there was a gradation through the black edge effect to the grey glaze and finally on to a thick green celedon. The red blush and the black edge effect were enhanced by the gas refiring. In the compound image at left all of the sections are examples of Blackwood ash glaze. None of the examples have been refired. The slightly olive section at bottom right is the result of some oxidation in the anagama firing. Neither of the two sections on the left changed toward olive during gas refiring. The grey section at top right of the image also was unaffected by gas refiring, and this was a major concern. This color can be quite common in Blackwood firings, and it turned out that the only thing we can think of to do  is to try to avoid it.

To avoid widespread occurence of the grey Blackwood ash glaze we have concentrated on encouraging situations where the Blackwood ash glaze rapidly changes from thick celedon to red blush or bare clay. These stacks of narrowly separated plates or bowls are useful, as is upside down packing, and the use of shields.  We do not usually refire anagama pots with gas, nor do we refire anagama  pots in the anagama, as our main allies in controlling the thickness of the natural ash glaze are the flame paths themselves, and we do not want to confuse the issue with conflicting flame paths from consecutive firings. Because of the physical shape of seashells, and the presence of sodium ions in  their composition, they are very useful in guiding flame paths while at the same time encouraging red blushes as result of the sodium.
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