Here are the results of what I hope will be the final glaze tests of this MA.! I dont intend to use every colour on every composite piece, but anyone will be free to. Instead I am likely to group them thus All but the dark green, the dark blue and maybe the teal will have a darker colour in the grooves /dots to emphasise the pattern. The results of testing copper containing glazes (one thin layer brushed on and sponged off) then the glaze colours on top, fired to 1260C were good, but the corresponding tests using the dark blue (cobalt, manganese and tin) glaze were disappointing. Here is an example using glaze 30; it contains CTM stain no.1, rutile, tin and lithium. The glaze test furthest right (in both sets, above and below) is over a dark blue. Glaze 4/17 contains chrome 0.2, 30 contains 5 of tin, so I was surprised not to see a colour change, but although there is no hint of pink or brown, its not a successful glaze combination. Glaze 4a has copper and just a small amount of cobalt carbonate; 20 is 17 with three times as much copper. The problem observed in the two test tiles on the right could of course be caused by the tin oxide content. However this set of teal (6/3) does not show a problem over 6/31a which also contains tin; though none of them show a significant difference to the 6/3 (second from right) by itself.
The base glazes containing copper all appear to work well, so I will not be pursuing cobalt as an alternative.
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AuthorI am indulging my passion for ceramics by undertaking studies for an MA at UCLAN Archives
August 2021
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