The perfect storm of high surface tension and high LOI: Blisters.

Monday 8th April 2013

An example of how insight-live.com/material/173">calcium carbonate can cause blistering as it decomposes during firing. This is a cone 6 Ferro Frit 3249 based transparent (G2867) with 15% calcium carbonate added (there is no blistering without it). Calcium carbonate has a very high loss on ignition (LOI) and for this glaze, the gases of its decomposition are coming out at the wrong time. While there likely exists a firing schedule that takes this into account and could mature it to a perfect surface, the glaze is high in MgO, it has a high surface tension. That is likely enabling bubbles to form and hold better.

Pages that reference this post in the Digitalfire Reference Library:

Calcium Carbonate, Firing: What Happens to Ceramic Ware in a Firing Kiln, Two transparents having opposite melt fluidity/surface tension balances, Decomposition, Surface Tension, Glaze Blisters

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.