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This is GR6-L, is the standard GR6-A Ravenscrag Slip cone 6 base recipe + 10% chrome tin stain (the body is Midstone, the inside glaze is G2926B, the firing schedule is C6DHSC). Chrome tin stains are picky about their host glaze, if it does not have a compatible chemistry they fire grey. Obviously, there is a love affair going on here! But the mug on the left has an issue. The glaze on the left has gone on in varying thicknesses and these are producing crystallizations and runs and the incising is not being highlighted. The one on the right is under control. What is the difference? The rheology of the slurry for the bad mug was wrong - the specific gravity was too high (the water content was too low). Even on a quick dip it was building thickness unevenly and way too fast. And there were drips that were so big they had to be shaved off with a knife! After the addition of a lot of water, to take the specific gravity from 1.55 to 1.45 it was watery enough to accept some Epsom salts to make it thixotropic. The difference was amazing, it went on totally smooth without a single drip, producing the result on the right.
Articles |
Formulating a Clear Glaze Compatible with Chrome-Tin Stains
In ceramics color is often a matter of chemistry, that is, the host glaze must be compatible and have a sympathetic chemistry for the stain being added. Chrome-tin stains are a classic example. |
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Glossary |
Thixotropy
Thixotropy is a property of ceramic slurries of high water content. Thixotropic suspensions flow when moving but gel after sitting (for a few moments more depending on application). This phenomenon is helpful in getting even, drip-free glaze coverage. |
Glossary |
Rheology
In ceramics, this term refers to the flow and gel properties of a glaze or body suspension (made from water and mineral powders, with possible additives, deflocculants, modifiers). |
Glossary |
Glaze thickness
Many ceramic glaze benefits and issues are closely related to the thickness with which the glaze is applied. Many glazes are very sensitive to thickness, so control is needed. |
Recipes |
GR6-L - Ravenscrag Cone 6 Transparent Burgundy
A stain-based method to achieve this color using the Ravenscrag base recipe. |
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