How do I fix pinholes and blistering in glazing?

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How do I fix pinholes and blistering in glazing?

The first thing to check is to make sure you are not putting on too thick a layer of glaze.

Another common cause of pinholes and blistering is the firing cycle that does not match the particular clay that you are firing. Some of things in clay such as organic materials, sulfuric compounds, manganese and anything else that needs to out gas during the bisque process must be completely burned out during the bisque process. If it is not completely burned out then it may out gas during the glaze cycle and cause pinholes and blistering.

First of all try using the standard Slow Bisque program on your control. If this still does not work then create a Vary-Fire or Custom program that will slow the bisque firing down.

Here is an example of a typical Vary-Fire program that has been known to work well firing to Cone 05. See the Appendix E in the DynaTrol Instruction Manual for other base programs and temperatures if you are bisquing at different cones. Note that we are combining the segment that goes from 1000°F to 1100°F and the following segment in the typical bisque programs and are using a very slow ramp rate for both.

Number of Segments: 4

Segment Number

Rate of Rise in Deg F per Hour

Temperature Set Point (Deg F)

Hold Time

1

80

250

00.00

2

200

1000

00.00

3

100

1641

00.00

4

80

1891

00.00

Note you can add a PreHeat by adding another segment before this (using a total of 5 segments) with a Ramp of 40°F per hour to 200°F and hold for some time (at least one to two hours long (01:30 to 02:00)