Glaze tests – high firing

Tests no.1 and 2 below are the same Blue grey speckle glaze as seen in the previous post with low firing tests. Here I fired them to 1260C rather than 1060C to find out what happened to earthenware glazes at stoneware temperatures. 1 is the glaze on Buff stoneware clay while 2 is on porcelain. I still don’t like the results but maybe this glaze will look better layered with others.

In contrast I really like the opaque speckled green glaze from Emmanuel Cooper’s ‘Potter’s book of glaze recipes’. It has lots of depth on the Buff stoneware (4) and breaks to a warm orange when applied thinly. I like the celadon colour effect on porcelain too (3).

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Opaque speckled green stoneware glaze (1200-1220C)

Clear transparent glaze base:
Standard borax frit                         30
Feldspar                                             25
Calcium borate frit                           5
Ball clay                                             20
Flint                                                    20

with addition of :
Tin oxide                                          5%
Copper carbonate                          1.5%

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