A promising glaze result is useful. A result you can reproduce is far more valuable. Advanced ceramic testing requires separating variables, documenting heatwork, and understanding how a glaze responds to both application and kiln conditions.
Begin with a clear testing question
Avoid asking whether a glaze simply “looks good.” Ask something measurable: Does an additional coat increase running? Does this glaze break differently over texture? Does the same recipe look different on porcelain and stoneware?
Write down the hypothesis before loading the kiln. Define what success means: surface quality, color, movement, fit, or consistency.
Build a controlled test-tile matrix
Use standardized tiles with similar dimensions, texture, and orientation. Include a catch area for glazes that may run. Label every tile with a durable code that survives firing.
For example, test one glaze on two clay bodies at two application thicknesses. That produces four combinations. Add repeat tiles if you need to assess variation. Do not change the firing schedule at the same time unless it is deliberately part of a separate experiment.
Measure application consistently
“Three coats” is not always a reproducible measurement. Brush loading, glaze viscosity, and drying between coats affect deposited material. When appropriate, record tile weight before and after glazing once the application is dry, alongside the method used. For dipping, track specific gravity or other relevant slurry measurements when your process supports them.
Record actual kiln conditions
Kiln programs describe intended firing conditions, not necessarily the heatwork every shelf experiences. Place witness cones in representative locations, following safe kiln practices, and document shelf position, load density, peak program, holds, and cooling schedule.
A glaze that behaves differently near the top of a kiln may be responding to temperature distribution or cooling differences rather than a recipe problem.
Evaluate more than appearance
Inspect test tiles for running, crawling, pinholes, crazing, shivering, and surface texture. Consider glaze fit and durability separately from visual appeal. Attractive results do not automatically establish food-contact suitability. Use appropriate testing and materials guidance before placing experimental glazes on functional ware.
Repeat your best result
Before adopting a new glaze combination for production, repeat the strongest test in another firing. If possible, include a known reference tile to compare kiln behavior across loads. Repeatability is the standard that turns a lucky outcome into a dependable studio process.
Make The Potter's Mud Room your testing record
The Potter's Mud Room helps potters organize test tiles, glaze details, piece photographs, firing histories, and Studio Notes in one place. That makes it easier to trace a successful result back to the exact clay, glaze application, and firing context—and to spot patterns when a later batch behaves differently.
Takeaway: Strong glaze research depends on controlled comparisons, detailed records, and repeated confirmation. Your next reliable result starts with a well-designed test.