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Ravenscrag Cone 6 Clear Glossy Base

Code: GR6-A
Modification Date: 2017-08-08 14:53:07
Member of Group: RV6

This Plainsman Cone 6 Ravenscrag Slip base it just the pure material with 20% added frit.

MaterialAmount
Ravenscrag Slip50.0
Calcined Ravenscrag Slip30.0
Ferro Frit 313420.0
 100.00  

Firing Schedule

Rate (F)Temp (F)Hold (Min)Step
100220601
300173302
1082175153
1502075304

Notes

This is the base cone 6 Ravenscrag recipe, it fires as a transparent glossy (with some variegation from coarser particles that produce some fine specks and a small amount of iron that imparts a blush of amber color). It is most glossy at a complete cone 6 (for a lower temperature just increase the frit a little).

As a transparent, this glaze it is best suited for use on light-burning stonewares (e.g. Plainsman M340). On whiter porcelains it may not fire clear enough. On darker clay bodies it may be too cloudy. Is has a low enough thermal expansion to fit most bodies. For porcelains or white stonewares consider using G2926B or G3806C instead.

However this is best as a base recipe, it is best suited to additions of opacifiers, variegators and colors. Add zircopax to get a white (about 10%). The white produced should be somewhat variegated and, depending on percentage, will be more transparent on the edges of contours (and thereby highlight them). For even better variegation, add some titanium dioxide (1-2% to a mix already containing 6-8 zircopax). The titanium both opacifies and variegates.

You can also add colorants and variegators (with or without opacifier). If colorant additions affect melt fluidity, add or reduce the frit content to compensate.

If you get cracking of the glaze during drying, increase the calcine clay at the expense of raw clay.

Calcining Ravenscrag Slip

Calcining Ravenscrag Slip

This is Ravenscrag Slip, I am going to calcine about 10 pounds of it in this bisque ware vessel to destroy the plasticity. I will fire to 1000F and hold it for 2 hours to make sure the heat penetrates. Why calcine? Because I have found that in some glazes having 70% or more Ravenscrag Slip, cracking on drying can occur if it is applied too thick. I love the working properties of these glazes and want to optimize them to avoid any problems. I am going to mix 75:25 raw:calcine on the next batch of glaze. However, Ravenscrag has an LOI of 9%, so I need to use 9% less of the calcine powder (just multiply the amount by 0.91). Suppose, I needed 1000 grams: I would use 750 raw and 250*.91=227.5.

Cone 5R mug with GR6-A Ravenscrag glaze

Cone 5R mug with GR6-A Ravenscrag glaze

Ravenscrag Slip at cone 5R and 10R

Ravenscrag Slip at cone 5R and 10R

Cone 5 GR6-A glaze at cone 5R on Plainsman M340 (left) and pure Ravenscrag Slip at cone 10R on H550 (right).

Ravenscrag Slip transparent and Alberta Slip blue glazes by Tony Hansen

Ravenscrag Slip transparent and Alberta Slip blue glazes by Tony Hansen

The mug is the buff stoneware Plainsman M340. Firing is cone 6. On the inside is the GR6-A Ravenscrag transparent base glaze. The outside glaze is GA6-C Alberta Slip rutile blue on the outside. The transparent, although slightly amber in color compared to a frit-based transparent, does look better on buff burning stoneware bodies this.

Out Bound Links

In Bound Links


By Tony Hansen

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