Six Easy Steps to Stop Glaze Shivering

Glaze shivering on a high-fire stoneware bowl, cone 9 (2300ºF), reduction firing.

Though not as common as some other glaze defects, shivering is a severe problem that occurs when the glaze is under too much compression as it cools in the kiln. When the glaze is in the liquid state during the firing process, it fits the clay body like warm honey; however, when the glaze cools, it compresses at a greater rate than the underlying clay body.

Shivering looks like a paint chip and can range from 1/16 in. to more than 2 in. Frequently, when a glaze peels off, it does so at the pot’s edges or raised areas of the pottery. With any correction, the goal should be to have the glaze and clay body cool at compatible rates, with the glaze coming under slight compression.

Shivering can happen when the pots are removed from the kiln or sometimes years later. It can occur in hydrocarbon-fueled kilns, such those fired by natural gas or propane, when a reduction atmosphere (excess fuel-to-air ratio in combustion) is introduced too early or too intensely in the firing, causing an unstable carbon bond between the clay and glaze layer. Glaze shivering can also take place in an oxidation electric kiln atmosphere at any temperature range.

In addition, clay bodies containing too much free silica can cause shivering; specifically, fireclays (as a group) are known to have randomly high levels of free silica. Fine grog that contains high levels of silica can also be a potential cause of shivering, especially if burnishing has brought it to the clay surface in the forming process. Sometimes tapping the suspect pot on its edge can induce the glaze to flake off. Thicker glaze applications are more likely to encourage shivering if any or all of the previous conditions are present. Conversely, a thinner glaze application can inhibit shivering, but it does not cure the underlying cause of the problem (too much compression in the fired glaze).

It is important to note that if one clay body and glaze shivers, all of the other pottery with the same clay body/glaze combination should be suspect of potential shivering.

Detail of glaze shivering, low-fire cone 06 (1828ºF), oxidation firing.

Although shivering is classified as a glaze defect, it can be corrected through adjustments to the glaze formula, the clay body formula or a combination of both. The following six steps are recommended to correct shivering.

1. If only one glaze is shivering on the clay body, try additions of 5, 10 or 15 parts of feldspar or frit, whichever is contained in the original glaze formula (i.e., if the glaze has 10 parts feldspar, increase that amount to 15, 20 or 25 parts). Do not change the amounts of other materials in the glaze. Other alkali-bearing materials, such as frits, can be used to correct shivering, but keep in mind that frits can lower the melting point of a glaze. Adding too much of any flux or glass former will increase the chance of the glaze becoming glossy or running off vertical surfaces. The ideal fix is to put just enough feldspar or frit into the glaze to correct shivering without overloading the glaze with more flux than is needed.

2. Decreasing the flint in the glaze by 5 or 10 parts will also adjust the clay body/glaze fit.

3. Occasionally, adding feldspar/frit and removing flint will be a necessary to stop shivering. In rare instances, the same correction must be carried out in the clay body.

4. If many different types of glazes are shivering on the same clay body, correct the problem by adding, 5, 10 or 15 parts feldspar (or other alkali-bearing materials) to the clay body.

5. A decrease of 5 or 10 parts flint in the clay body may also correct glaze shivering.

6. If a commercial glaze shivers, it is often easier to find another glaze that looks the same, or use a different clay body with the expectation that an unrelated combination of glaze and/or clay will achieve a better fit.

Shivering can occur any time a glaze is under extreme compression. In the examples shown here, notice how the glaze peels away, exposing the underlying clay body.

Did you enjoy this article? Click here to subscribe to Ceramic Industry Magazine.

Recent Articles by Jeff Zamek

You must login or register in order to post a comment.



Image Galleries

2015 Ceramics Expo

Snapshots from the 2015 Ceramics Expo, April 28-30, Cleveland, Ohio. Posted: May 14, 2015.


Ceramics Expo podcast
Editor Susan Sutton discusses the upcoming Ceramics Expo with event director Adam Moore.
More Podcasts

Ceramic Industry Magazine

June 2015 ceramic industry

2015 June

This issue features our first annual Supplier of the Year Awards. Be sure to check it out!
Table Of Contents Subscribe

Daily News

We know where you find the latest ceramic industry news (ahem), but where do you catch up on the rest of your daily news?
View Results Poll Archive


M:\General Shared\__AEC Store Katie Z\AEC Store\Images\Ceramics Industry\handbook of advanced ceramics.gif
Handbook of Advanced Ceramics Machining

Ceramics, with their unique properties and diverse applications, hold the potential to revolutionize many industries, including automotive and semiconductors.

More Products

Clear Seas Research

Clear Seas ResearchWith access to over one million professionals and more than 60 industry-specific publications,Clear Seas Research offers relevant insights from those who know your industry best. Let us customize a market research solution that exceeds your marketing goals.


facebook_40px twitter_40px  youtube_40pxlinkedin_40google+ icon 40px


CI Data Book July 2012

Ceramic Industry's Directories including Components, Equipment Digest, Services, Data Book & Buyers Guide, Materials Handbook and much more!