curt

close up of the plaster mold I use to make my currie tiles. Basically just a flat plaster bat which I carved in to using a ruler and some standard turning/trimming tools. If (when?) I do this again I will use a much smoother bat (this one was a re-purposed clay drying bat) and make the cells larger. That said, the scale of this bat was chosen to make it fit exactly into my small electric test kiln.

Cone 10 reduction. Mains gas. BRT with porcelain slip and 3 different ash glazes.

clear glaze with copper carb cone 10 Oxidation. 800x magnified and backlit. The large measuring mark is a 1 millimetre mark, the small marks are one tenth of a millimetre. Bubbles are about one tenth of a millimetre and are not visible to the naked eye.

Clear glaze with copper carbonate at cone 10 and magnified 200x. The large hash marks are millimetres and the small has marks are tenths of a millimetre, so the bubbles here are about a tenth of a millimetre and not visible to the naked eye.

the glass of the glaze appears well developed here, dark and clear behind the bubbles. celadon glaze

these bubbles are definitely much more numerous, and somewhat larger than on the walls of the pot where the glaze was flowing well. This is a celadon glaze

the craze line from the accompanying picture is visible on the left side

the glaze bubbles in the accompanying close up picture are right in the centre of this one near the craze line

Local barytes testing. Currie test tile format. Fired in mid-size LPG gas fibre kiln, cone 10, heavy reduction from 900 to 1280, then a very clean 30 min soak in oxidation. This cell is night and day to its twin fired in oxidation. There is evidence of good melting in most cells, probably much of this due to the high iron content of the barytes. I am left wondering if there is some other flux here besides just the iron which works well in reduction (in addition to the barium sulphate of course) While the well melted zone is about where expected, there is a real difference in surface quality between, for instance, column 2 and column 3, and then again between column 3 and column 4. This suggests (to me at least) that there is a fairly specific quantity of silica which this barytes can absorb into the melt, as the surfaces are all matte-ish in column 2, well melted in most of column 3 (including right at the bottom with no clay!), and clear evidence of silica overload in most of column 4.

Local barytes testing. Currie test tile format. Fired in small electric test kiln, Cone 10 oxidation. Amazing to see that there is virtually no melting in any of these cells. In fact the only evidence of any melting at all is around cell 31, and even then only just a little. Now compare to the same tile fired in reduction. (Note: this image is unadjusted)

basalt test. heavy reduction, cone 10. mostly still whole particles of what started as 40 mesh material. however, in spite of its appearance, this sample has fused together somehow internally and is not able to be removed from the test dish.

this photo was taken in overcast conditions with an Iphone with AE adjustment targeting the tile.

This photo was taken in overcast conditions with an Iphone with no adjustments

Bottom right corner, no clay, high silica. some overload of the silica (basalt) clearly showing up near the corner and above it.

Bottom left corner, mostly flux. very interesting resilience of the "striding man" here. Seems like where the kaolin addition is thicker it has not been fully absorbed into the melt....or ?....

Upper right corner, high clay, high silica, (supposedly) much less flux. Still looks pretty fluxy to me though...

Upper left corner high clay, little silica

Full Tile. Lots of crazing... and spitting! I have used basalt instead of silica.