Rutile in functional glazes: Push the limit and you might get this

Wednesday 3rd August 2011

The 80:20 GA6-A insight-live.com/material/32">Alberta Slip base becomes oatmeal-like when oversaturated with rutile and/or titanium (left: 6% rutile + 3% titanium dioxide; right: 4% rutile + 2% titanium dioxide). The rough surface results from excessive crystallization of titanium-bearing phases from the melt during cooling. It is unpleasant to touch, readily shows cutlery marking and is less desirable for functional surfaces. In glazes of this type, rutile additions above about 4% can become increasingly difficult to keep smooth and consistent. Crystallization, rather than phase separation, increasingly dominates the variegation mechanism.

One way of avoiding problems is staying below the tipping point, keeping the percentage as low as possible while still getting the desired variegation (of course, that will vary depending on the melt fluidity of the glaze and kiln cooling). Surprisingly, making the glaze more fluid does not necessarily solve the problem. Greater melt fluidity increases ion mobility and can actually promote crystal growth during cooling, producing an even rougher surface.

Pages that reference this post in the Digitalfire Reference Library:

Ceramic Rutile, GA6-F - Alberta Slip Cone 6 Oatmeal, Opalescent glazes, what are they, High-titanium glazes: Great on a test tile, troublesome on ware, Leaching, Crystallization, Food Safe, Rutile Blue 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.