Both pieces are the same clay body, Plansman L215. Both are fired to cone 03. Both are glazed using G1916Q recipe. The glaze on the piece on the left has 2% added iron oxide (and sieved to 80 mesh). Each grain of iron (which is refractory in this situation) acts to congregate the micro-bubbles so they can move through the glaze layer. Notice also how much richer the color is on that piece. The piece on the right does not have added iron oxide. It is not as red and not as transparent. Both of these mugs, by the way, are glazed on the bottom and were fired on stilts.
G1916Q - Low Fire Highly-Expansion-Adjustable Transparent
An expansion-adjustable cone 04-02 transparent glaze made using three common Ferro frits (low and high expansion), it produces an easy-to-use slurry.
|Materials||Iron Oxide Red|
Suspended micro-bubbles in ceramic glazes affect their transparency and depth. Sometimes they add to to aesthetics. Often not. What causes them and what to do to remove them.