GR6-A - Ravenscrag Cone 6 Clear Glossy Base

Modified: 2023-04-15 23:01:04

This Plainsman Cone 6 Ravenscrag Slip base is just the pure material with 20% added frit to make it melt to a glossy natural clear.

Material	Amount
Ravenscrag Slip	50.00
Ravenscrag Slip 1000F Roast	30.00
Ferro Frit 3134	20.00
100.00

Notes

Also known as G2936C.

This is the base cone 6 Ravenscrag recipe, it fires as a transparent glossy. It has an addition of the most common North American borate frit, enough to produce a good glass at cone 6. Most other glazes based on Ravenscrag use this as a starting point (although they might substitute the frit for another).

The character of this is not the same as transparent glazes made from materials like feldspar, kaolin, silica, wollastonite and frit. This is a natural clay material having some iron content and particles you can feel (up to 42 mesh). So it forms a less sterile glaze, one having some variegation, fine speckle and slight blush or amber coloration. It is most glossy at a complete cone 6 (for a lower temperature you may need to increase the frit a little).

It is best to at least hold the temperature at the end of the firing to minimize firing defects. Even better, use the C6DHSC firing schedule.

As a transparent, this glaze is best suited for use on light-burning stonewares (e.g. Plainsman M340). On whiter porcelains and stonewares, it may not fire to a sufficiently transparent glass (consider using G2926B or G3806C instead). On darker clay bodies this recipe may fire too cloudy. Is has a low enough thermal expansion to fit most bodies, but if it does craze consider substituting Ferro Frit 3195.

As noted, this is a base recipe, well suited to additions of opacifiers, variegators and colors. Add zircopax to get a white (about 10%). The white produced will be somewhat variegated (non-toilet-bowl-like). For variation-with-thickness, to highlight edges of contours, use a lower percentage of zircopax. For even better variegation, add some titanium dioxide (1-2% to a mix already containing 6-8 zircopax). Add colorants and variegators (with or without opacifier). If colorant additions affect melt fluidity, add or reduce the frit percentage to compensate.

If it cracks during drying, increase the roast clay at the expense of raw clay.

Glazes having a high percentage of Ravenscrag Slip are most often prepared using the traditional method of simply adding water until the preferred viscosity is achieved (the material has inherent properties that produce functional slurries for dipping). Control of drying shrinkage and slurry character is achieved by varying the proportion of roast and raw powder in the recipe. For us, a weight ratio of 80 water to 100 powder (2000 water for 2.5kg of powder) produces a 1.5-specific-gravity slurry that, although fairly runny, gives the right thickness on 1-2 second dip on 1850F bisque-ware (there is some dripping, but coverage is even and it is quick-drying). This recipe actually does not respond to flocculant additions that gel traditional mineral-blend glazes to a thixotropic state.