Manually program your kiln or suffer glaze defects!

To do a drop-and-hold firing you must manually program your kiln controller. It is the secret to surfaces without pinholes and blisters.

B. Glazes

Click here to watch this at or click here to go to our Youtube channel

There is no other way to do a drop-and-hold firing but manually program your computer controller.

What is drop-and-hold? It is a firing that holds at the top temperature only long enough to even out the heat, then drop one hundred degrees (or what is appropriate for your glazes) and hold the temperature there (e.g. half an hour)

Why should you do this? Crystalline glazes. Rutile glazes develop much better. But there is a much more important example. If you are using bodies that contain particles that produce gases during firing these have to escape. If they are generated after the glaze melts, they have to bubble through it. If the latter is not able to heal a pinhole will result, if it partially heals you could have a blister and if it almost heals a dimple. Materials in the glaze itself also gas, some quite late in the firing. The problem with soaking at top temperature is that reactions that produce gases are ongoing, bubbles just keeping coming. Some bodies have so many particulates that gas during latter stages of firing that it is almost impossible to fire defect-free glazes on them. This is particularly true with low temperature terra cotta bodies. But using this technique completely solves the problem! You might think that the glaze will not be fluid and mobile enough to smooth out but most glazes, especially those with boron, begin to melt far lower than you might think. Ideally one should try different drop-and-hold temperatures to arrive at one that is a good compromise between sufficient glaze melt mobility and maximum reaction shut down.

Manually programming a typical electric hobby kiln electronic controller

Manually programming a typical electric hobby kiln electronic controller

I document programs in my account at, then print them out and enter them into the controller. This controller can hold six, it calls them Users. The one I last edited is the one that runs when I press "Start". When I press the "Enter Program" button it asks which User: I key in "2" (for my cone 6 lab tests). It asks how many segments: I press Enter to accept the 3 (remember, I am editing the program). After that it asks questions about each step (rows 2, 3, 4): the Ramp "rA" (degrees F/hr), the Temperature to go to (°F) to and the Hold time in minutes (HLdx). In this program I am heating at 300F/hr to 240F and holding 60 minutes, then 400/hr to 2095 and holding zero minutes, then at 108/hr to 2195 and holding 10 minutes. The last step is to set a temperature where an alarm should start sounding (I set 9999 so it will never sound). When complete it reads "Idle". Then I press the "Start" button to begin. If I want to change it I press the "Stop" button. Those ten other buttons? Don't use them, automatic firing is not accurate. One more thing: If it is not responding to "Enter Program" press the Stop button first.

In Bound Links

  • (Glossary) Bisque, bisquit firing

    Generally, bisque firing refers to the practice of prefiring ware without glaze to make it impervious to water, resistant to damage during handling and absorbent for glazing. The porosity of the bisque (generally more than 15%) makes it an ideal medium to absorb water from the glaze suspension and h...

  • (Glossary) Firing Schedule

    In most electric periodic kilns firing schedules are programmed into electronic controllers to control the rate-of-rise, soaking time and often the cooling curve. In industry firings are very fast, optimization of every stage is absolutely critical, in hobby ceramics and small companies firings are ...

  • (Glossary) Firing

    At it most basic level, firing is process of heating a clay (or recipe of clays and minerals) to a temperature sufficient to fuse the particles together. However today, each type of ceramic has its not only its own firing temperature, but also schedule (control of the rate of rise and fall of the ki...

  • (Glossary) Pinholing

    A glaze defect where tiny holes are present in the fired glaze surface. These holes normally go down to the body surface below. Pinholing is a plague in industry, the tiniest hole in the glaze surface of a tile or utilitarian item can make it a reject. Industry goes to great pains to get materials o...

  • (Troubles) Glaze Blisters

    Questions and suggestions to help you reason out the real cause of ceramic glaze blistering and bubbling problems and work out a solution

  • (Troubles) Glaze Pinholes, Pitting

    Analyze the causes of ceramic glaze pinholing and pitting so your fix is dealing with the real issues, not a symptom.

  • (Glossary) Soaking

    The practice of holding the kiln at final firing temperature for a period of time. This is usually done to mature the clay (especially if the firing was fast) and give the glaze opportunity to flow and heal imperfections. Soaking in a firing schedule should normally be accompanied by a slower approa...

By Tony Hansen

Feedback, Suggestions

Your email address


Your Name


Copyright 2003, 2008, 2015, All Rights Reserved