cwells Posted March 9 Report Share Posted March 9 (edited) Hi all, I started potting as a hobby about a year ago. A couple weeks ago, I got into glaze making and decided to try to make my own matte base as an exercise, after consuming all of the free information I could. It seemed to have worked well, as I got the desired effect of a cone 6 matte black. I followed all of the information I could find, and made sure it was 0.3:0.7 alkali:alkaline metals, 0.16 boron, and it charted on the stull map as a matte at 0.74 alumina and 2.54 silica. At that time, I did not fire a test tile without the colorants. I replaced some of the EPK with calcined EPK as I was having some crawling issues with application, and made two more test tiles. Where I'm confused, i tried to fire the base without the added colorants, and fired the two test tiles together. One with 8% yellow iron oxide, one with no iron. The one with the iron fired nicely and seems durable to the eye (added cobalt didnt seem to dissolve when soaked in acids, glass didn't seem to erode in bases, and doesn't scratch or chip). The one without the iron is a dry brittle glaze that I can flake off with a pin tool, so I assume it's underfired. From what I understand, in oxidation fe2o3 should have a higher melting point than cone 6, and doesn't give off it's oxygen until cone 7-8 to become feo. I'm not sure where my misunderstanding lays, does iron oxide act as a flux in cone 6 oxidation, or am I missing something else entirely? Thanks! Edited March 9 by cwells grammar Quote Link to comment Share on other sites More sharing options...
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