Kiln Firing Guidelines

General Information

What this Guide represents:

The Firing Guide is designed to provide experienced users with a general guide for a wide variety of kiln firing projects. It is expected that users with specific needs will make modifications to suit their project and circumstances, particularly in the heating steps. The recommendations assume that most cooling is occurring from the exposed top side (if any), and that the bottom side is supported on a shelf or shelf system above the kiln floor, and therefore is insulating the glass a certain amount.

Limitations of the guidelines:

Size: These recommendations are for all sizes of firings, limited only by your kiln dimensions.
In general: This guide is not intended to cover all possible form and technique variations that will be conjured up by artists. It will cover many typical forms and mold systems, especially with typical adjustments as described below. This guide is not intended to be an instruction manual but a look up table. Please refer to current books on fusing or kiln firing, Uroboros Glass Skill Builders or other fused glass manufacturer's tip sheets, or to your instructor for detailed and specialized instruction. For unusual or high value projects, please contact Uroboros directly for more information.

How were the guidelines developed?

These guides were compiled by Eric Lovell, founder of Uroboros Glass, and rely on experience based modifications of theoretical 2 sided annealing & cooling tables. Many of the individual thickness recommendations have been tested by users, and the results have been proven successful. Successful firings means that not only were there no cracks in the one or more pieces of a given thickness and form over an extended period of time, but also through reasonable temp cycling, during grinding and polishing, and/or the finished work was examined for stress polariscopically.

Uroboros would like to particularly thank the following for their input and valuable perspective: William Ward, Paul Marioni, Roger Thomas, Walter Gordinier, Henry Halem, Michael Behrens, Gerry Newcomb, Melanie Rowe, Leslie Rowe-Israelson, Gil Reynolds, Patty Gray, Hartmut Glenewinkel, Michael DuPille & Lucartha Kohler.

These guidelines will evolve as new experiences occur. You can contribute!

We invite you to make a contribution to future updates of this guide, particularly for unusual forms and sizes. Just send us a description or photo of your finished work, along with the firing schedule used, kiln type, and how you determined the firing to be successful. Sorry, "Because it didn't break the first week" isn't enough to indicate success for this purpose.