The perfect storm to create boron-blue clouding at low fire

Saturday 18th July 2015

Two clear glazes fired in the same slow-cool kiln on the same body with the same thickness. Why is one suffering insight-live.com/glossary/129">boron blue (1916Q) and the other is not? Chemistry and material sourcing. Boron blue crystals grow best when there is plenty of boron (and other power fluxes), alumina is low, adequate silica is available and cooling is slow enough to give them time to grow. In the glaze on the left B2O3 is higher, crystal-fighting Al2O3 and MgO levels are a lot lower, KNaO fluxing is significantly higher, it has more SiO2 and the cooling is slow. In addition, it is sourcing B2O3 from a frit making the boron even more available for crystal formation (the glaze on the right is G2931F, it sources its boron from Ulexite).

Pages that reference this post in the Digitalfire Reference Library:

Ulexite, Boron Blue, Crystallization, Clouding in Ceramic Glazes

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.