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GR6-L - Ravenscrag Cone 6 Transparent Burgundy

Modified: 2024-03-17 23:31:59

A stain-based method to achieve this color using the Ravenscrag base recipe.

Notes

This is an excellent alternative to the GR6-E Raspberry recipe. It is simpler, just a stain addition to the standard transparent. It is more reliable. It is easy to adjust the amount of stain to get the exact shade you want. This base recipe is unusual in that it supports the development of chrome tin stains, these are available in many shades from pink to red, consider trying a different another if this color is not right for you.

Because this is transparent (contains no opacifier), different thicknesses have different intensities of color. Because it employs a stain it will be more consistent than one using chrome and tin. Add an opacifier, like titanium, to create a more pastel color with variegation (e.g. 2-4%).

No special firing curve is needed and the surface fires very clean and defect free (with a normal soak at cone 6, or even better, the C6DHSC schedule).

For mixing instructions please see the master recipe, GR6-A.

Related Information

A breaking glaze highlights incised decoration by its variation in thickness

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This is the Ravenscrag slip cone 6 base (GR6-A which is 80 Ravenscrag, 20 Frit 3134) with 10% Mason 6006 stain (our code GR6-L). Notice how the color is white where it thins on contours, this is called "breaking". Thus we say that this glaze "breaks to white". The development of this color needs the right chemistry in the host glaze and it needs depth to work (on the edges the glaze is too thin so there is no color). The breaking phenomenon has many mechanisms, this is just one. Interestingly, the GR6-A transparent base has more entrained micro-bubbles than a frit-based glaze, however these enhance the color effect in this case.

Ravenscrag Cone 6 Raspberry glaze on light and dark burning bodies

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This is GR6-L Ravenscrag Raspberry glaze fired at cone 6 using the C6DHSC schedule. The body on the left is Plainsman M340. On the right is Coffee Clay. The black burning color of the Coffee Clay is due to a 10% raw umber addition, the manganese in the umber interacts on edges where it is thinner.

Ravenscrag Cone 6 white glaze with 10% Mason chrome tin stain

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The body is Plainsman M340 and these two glazes are based on the GR6-A recipe (Ravenscrag Slip + 20% frit). The GR6-C creamy white glaze adds 10% Zircopax to opacify it. The pink version, our code number GR6-L, adds Mason 6006 stain instead. The GR6-A base is zinc-free and just hits the 10% minimum CaO recommended to get color development with a chrome tin stain. This recipe also couples a low MgO level (MgO can kill the color in chrome tin stains).

GR6-E and GR6-L Ravenscrag Pink glazes side-by-side

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The GR6-L (the two on the left) employs raw chrome and tin, the GR6-E uses a stain (Mason 6006). The L does not melt quite as well (because of the 10% whiting in the recipe to make sure it develops the chrome-tin color well). The GR6-E is does not need the whiting. The E is more flexible because one can choose different stains to get different colors. Of course the intensity of the color can be adjusted by varying the percentage of colorant. And the L could be made to melt better by increasing the percentage of frit.

Cone 6 GR6-E Ravenscrag Raspberry glaze

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Made using chrome and tin added to the cone 6 Ravenscrag clear base glaze recipe.

Maroon and white mug before and after firing: What a difference!

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The outer glaze is Ravenscrag GR6-E Raspberry, the bright maroon color is a product of the surprising interaction between the 0.5% chrome oxide and 7.5% tin oxide present. That small amount of chrome is only enough to give the raw powder a slight greenish hue, hardly different than the clear liner glaze. While this color mechanism appears to be effective, it is delicate. A maroon stain is actually a better choice. It would fire more consistent would be less hazardous to use. And the raw glaze will be the same color as the fired one!

Ravenscrag Raspberry on porcelain

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Plainsman P300 with GR6-L Ravenscrag raspberry glaze. This effect requires that it not be applied to thickly.

Bad and good glaze application: The difference was the rheology.

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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.

Links

XML to Paste Into Insight-live

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