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    Slips: Albany, Alberta, Sheffield     Clay, Ball Clays, Fire Clays, Fillers & Kaolin Clay & Glaze Chemicals
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Raw Materials / Slips: Albany, Alberta, Sheffield / Ravenscrag Slip

Ravenscrag Slip

Ravenscrag Slip can be viewed as a 'plastic feldspar' that provides good melting and excellent working properties in a light-colored material.

  • It is feasible to use Ravenscrag Slip 'as is' at cone 10, on either green or bisque-fired ware, to achieve a light-colored silky matte surface. 
  • We refer to Ravenscrag as a 'silty' material because, although it contains enough clay to give it some plasticity and dry hardness, it also contains a variety of other very fine mineral particles that do not interact with water the way clay particles do. The particles give it its melting and application properties.

Process Properties

  • A fundamental advantage of basing your slips and glazes on this material is its application properties.
  • Ravenscrag Slip contains more than 70% native silty clay.
  • A slurry glides onto the ware like silk, and you can apply multiple layers onto bisque or dry ware without drying cracks and crawling problems.
  • Even pure Ravenscrag Slip will resist crawling on sharp interior corners and edges.

Like Albany Slip, Ravenscrag Slip is excellent for underglaze use to achieve variegation and pooling effects (i.e. a dark glossy glaze under a more stable white). However, you will need to test to make sure that the overglaze does not 'pull' on the Ravenscrag Slip underlayer and compromise its dry bond with the body. Use this material as the base for each layer if possible.

Since Ravenscrag Slip is a silty material, it does not work well for burnishing.


Ravenscrag Slip is the opposite of Alberta or Albany Slip: The latter are low melting, plastic, and dark burning; this is higher melting, non-plastic, and light burning. It melts to a semi-matte surface at cone 10. Adding small amounts of feldspar (i.e. 5-10%) will make it flow better and add gloss. We have not had good success with boron frits for cone 10 oxidation use; these tend to produce an uneven blistered surface (although some users have found that gerstley borate is ok as a flux).

Adding about 10% Ferro 3134 frit for cone 6 will produce a similar melt. Increasing the frit to 20% will improve flow and add gloss further. You can add colorants (i.e. stains, metal oxides), variegators (i.e. 5% rutile), and opacifiers (i.e. 10% Zircopax) to create almost any effect.

Since it is basically a clay material, a significant amount of gas is generated during decomposition during melting. If not fired high enough and not fluxed adequately, very thick layers could tend to form unbroken bubbles in the glaze layer.

Unless well melted, this material does not smooth out as well on coarser stoneware bodies as on bodies made from refined kaolins, ball clays, feldspar, etc. Some stonewares seem to generate gases at the 'wrong time' during the firing cycle, and Ravencrag bubbles up badly if the firing schedule is not right.

It is important to remember: Ravenscrag is a base material on which to build slips and glazes. By itself, it is simply a milky glaze; it needs opacifiers, colors, and variegators to produce visually interesting surfaces.

information source:  Ravenscrag, ltd.


Color Product SKU Description Lbs Add
CRRAVSRaw Clay     Add
Raw Materials / Slips: Albany, Alberta, Sheffield / Ravenscrag Slip