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Making Glaze Testing Cones

Description

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)

Article

Joe Schmidt, lab technician at Plainsman Clays, developed the glaze testing cone, it is very practical. It is a standard shape and size that is always used, this serves well for comparison and documentation purposes.

Advantages

• 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.

Pattern

Use the link below to download the pattern file.

Related Information

An example of the value of a good glaze testing sample.

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These are made at Plainsman Clays in Alberta, Canada.

Preparing to make a glaze testing cone: cutting around the pattern

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In this picture a piece of cardboard is used as a template, you can download a pattern using the URL link on this page.

Making a glaze testing cone: applying the slip for the join.

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A viscous slip will make a better join and minimize the chance of water-splits developing at the edge of the overlap.

Making a glaze testing cone: finishing the join.

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With most clays no scoring is needed, the slip and pressure are enough to make a good join.

Making a glaze testing cone: Incising the surface

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Glaze thickness thins on the edges of the incised lines and thickens at their bases. This enables variegating glazes to showcase their visual effect with varying thickness. And these test the ability of opaque glazes to still cover well when the layer is thin.

Making a glaze testing cone: Stamping an identification.

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The code numbers get recorded with the pictures in our testing system (an account at insight-live.com).

Links

URLs	https://digitalfire.com/4sight/images/GlazeConePattern.pdf Glaze cone pattern - Plainsman Clays

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