Paul Gruner on tue 26 feb 08
Pictures are here:
These aren't pretty glazes - the goal was to find out which fluxes will
coax some purple out of manganese dioxide (MnO2) and which fluxes will
turn it brown. I mixed four different base glazes: one alkali, one with
calcium and boron, one with alkalis including lithium, and one with
calcium and magnesium based on the "Eggplant Semi-matte" that Sally Guger
posted (also similar to the "Watral Purple" that Tom King posted - Thanks
both of you.)
To the base glazes I added 1.5% MnO2, 3% MnO2, and 3% MnO2 plus 1% Cobalt
Carbonate. So there are 12 test tiles. I also tested Nickel in a Strontium-
Zinc based glaze.
Generally it seems that high Alkali glazes are good, calcium is bad, and
magnesium makes light purple crystals similar to Cobalt-magnesium. Also,
it seems that manganese doesn't make a great purple by itself - it's
better at shifting cobalt from blue to purple.
It's funny, but I blended together all of the leftover test glazes and
used it on the inside of a teacup. That was the best looking glaze of all.
It's also most likely to be a stable glaze - it meets almost all the
guidelines in MC6G.
There are more things I want to check, but it'll be a week or two before I
get a chance to do it.