Zircopax as a fining agent to de-bubble a stained glaze

Thursday 3rd August 2017

The cone 03 porcelain cup on the left has 10% Cerdec encapsulated stain 239416 in the G2931K clear base (this is not an underglaze with a transparent over it). The surface is badly orange-peeled because the glass is full of micro-bubbles that developed during the firing. Notice that the insides of the cups are crystal-clear, no bubbles. So here, they are a direct product of the presence of the stain. The glaze on the right has even more stain, 15%. Why isn't it even worse? It also has a 3% addition of insight-live.com/material/1724">Zircopax (zircon), which acts as a fining agent. As you can see, this makes a dramatic difference. Suppliers of encapsulated stains even recommend a zircon addition, but are often unclear about why. This is the reason.

The yellow on the right could be improved further with a slow-cool or drop-and-hold firing. And if the glaze was reformulated to use a later melting frit (so fewer bubbles even get trapped).

Pages that reference this post in the Digitalfire Reference Library:

Zircopax, Zircon, A light bulb moment in solving bubble clouding: The same black engobe with two transparent glazes., Orange Peel Surface, Encapsulated Stain, Glaze Bubbles, Ceramic Stain, Fining Agent

This post is one of thousands found in the Digitalfire Reference Database. Most are part of a timeline maintained by Tony Hansen. You can search that timeline on the home page of digitalfire.com.