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A high-nepheline, zero-silica cone 8 silky matte pottery glaze is cutlery marking and crazing. Let's take a closer look and determine why?
You can also watch this at Screencast-o-matic.com
In this seven-minute video I use my account at Insight-live.com to look at the chemistry of a popular online pottery glaze recipe to determine why it has issues.
I have the recipe on the clipboard and enter it using the interpret feature (pasting it into a box, doing a little fix-up, then importing it).
Then I verify that all materials are linking to the materials database and turn calculation on for that recipe.
Then I open a glaze of the same type right beside it, one that I already have experience with and know works well on the clay bodies I use. After that it is a matter of comparing the chemistries based on what is known about how oxides contribute to glaze properties, the adjusting the recipe to produce the desired change in the oxide chemistry.
Glossary |
Cutlery Marking
Ceramic glazes that mark from cutlery are either not properly melted (lack flux), melted too much (lacking SiO2 and Al2O3), or have a micro-abrasive surface that abrades metal from cutlery. |
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Troubles |
Glaze Crazing
Ask the right questions to analyse the real cause of glaze crazing. Do not just treat the symptoms, the real cause is thermal expansion mismatch with the body. |
Articles |
Trafficking in Glaze Recipes
The trade is glaze recipes has spawned generations of potters going up blind alleys trying recipes that don't work and living with ones that are much more trouble than they are worth. It is time to leave this behind and take control. |
You will see examples of replacing unavailable materials (especially frits), fixing various issues (e.g. running, crazing, settling), making them melt more, adjusting matteness, etc. Insight-Live has an extensive help system (the round blue icon on the left) that also deals with fixing real-world problems and understanding glazes and clay bodies.
By Tony Hansen Follow me on |
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