Master of Arts (MA)
Semester of Degree Completion
June M. Krutza
The purpose for this research was to develop cone 5-6 crystalline glazes which will provide the potter with well-formed and large-sized crystals.
This firing range was selected for two reasons. First, very little information is available on crystalline glazes at this temperature range; and secondly, an attempt at conserving energy is being made by firing at this lower temperature.
Data obtained through this crystal research was gained via a series of 10 test firings. The kiln used for the testings and developing of the firing schedule for the Cones 5-6 crystal glazes was a Unique Kilns Model 2430, having a maximum temperature of 2350°F.
Several firing schedules were developed and tested. The firing which seemed to provide the best results brought the glazes to their maturing temperature in seven hours. Once this maturing temperature was reached a 10 minute soaking period was provided to allow all of the ingredients to enter into solution. The kiln was then shut down and the temperature was held for 3½ hours with a variance in temperature of ± 20°F.
Of the twelve base glazes developed, four base glazes appeared to provide crystals with some consistancy. These four base glazes were II, V, XI, and XII. Their empirical formulas are as follows: […]
From the above mentioned base glazes, fourteen crystal glazes were developed which had produced crystals ranging from 0.5cm to 1.5cm in diameter.
These glazes were as follows: IIf, IIk, IIl, IIm, IIo, IIr, IIs, IIt, Va, VIIIa, XIc, XIId, XIIe and XIIf. […]
The majority of the glazes tested developed better crystal structures when fired at Cone 6; with a drop to a holding temperature which was 100°F below what the pyrometer read when Cone 6 went down; and a holding period of 3½ hours. It appears that those glazes which produced crystals with some consistancy contained either titanium dioxide or lithium carbonate.
Kishpaugh, Barry W., "Cone 5 - 6 Crystalline Glazes" (1978). Masters Theses. 3198.