•The secret to cool bodies and glazes is a lot of testing.
•The secret to know what to test is material and chemistry knowledge.
•The secret to learning from testing is documentation.
•The place to test, do the chemistry and document is an account at https://insight-live.com
•The place to get the knowledge is https://digitalfire.com
Making Glaze Testing Cones
Section: Glazes, Subsection: General
A standard shape and size of glaze test is important to be able to compare one test with another, especially over time (so that old tests look the same as new ones)
Joe Schmidt, lab technician at Plainsman Clays, has developed a glaze testing cone that is very practical. Perhaps more important, it is a standard shape and size that is always used, this serves very well for comparison and documentation purposes.
- They are easy to make.
- They are easy to photograph
- They are stable and less likely to tip over and break
- They stack well in boxes
- They display a glaze in a way that is akin to a piece of pottery or ceramic.
Steps to make these:
- Print the pattern and cut it out
- Roll the clay to 1/4 inch (6mm) thickness
- Cut the shape out of the clay using the pattern
- Apply a band of slip to one end and attach the other using a 15mm (1/2 inch overlap)
- Press the joint firmly together (use a stick on the inside to support) and press the indentations
- Dry the clay to leather hardness and carve a design on the side opposite the join (to show what it does on edges, in varying thickness around contours and on an uneven surface)
- Stamp the identification of the clay at the bottom
- Dry the testers carefully to avoid cracking
- Use a knife to trim off any sharp edges
- Bisque fire.
When dipping these in glaze consider the following:
- Dip down to within 15mm (1/2 inch) of the base
- Label clearly on the bare clay section
- Dip the top half again for a double-thickness.
Click here for a PDF file pattern that you can print out.
Preparing to make a glaze testing cone: cutting around the pattern
Making a glaze testing cone: applying the slip for the join.
Making a glaze testing cone: finishing the join.
Making a glaze testing cone: Incising the surface to provide variation.
Making a glaze testing cone: Stamping an identification.
An example of the value of a good glaze testing sample.
These are made at Plainsman Clays in Alberta, Canada.
By Tony Hansen
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