These are the clays from Stone Mountain I'll be testing, descriptions are from Stone Mountain website. To see examples of the color of the clay after firing see their website.
216 - Tan Speckled Stoneware - is a warm, buff-colored clay with medium-sized black speckles. Ideal for throwing and handbuilding, Tan Speck is smooth and rather plastic, and takes attachments with ease. It is easy-to-use and not very stiff, very beginner-friendly. 216 textures nicely, it provides a great surface for carving and the speckles will show through sheer and semi-opaque glazes. Its buff color may slightly warm sheer glazes, but typically will not drastically change a glaze's fired color. Tan Speck vitrifies (becomes water-tight) at Cone 6, and can be fired up to Cone 8 in oxidation.
246 - Speckled Brick Stoneware - is a deep reddish-brown clay with large, infrequent black specks. Ideal for throwing and handbuilding, Speckled Brick is smooth and rather plastic, taking attachments with ease. It is easy-to-use and not very stiff, very beginner-friendly. 246 textures nicely, it provides a great surface for carving and its subtle speckles will show through all sheer and most opaque glazes. Its deep color will warm sheer glazes, but typically will not drastically change an opaque glaze's fired color. Speckled Brick vitrifies (becomes water-tight) at Cone 6, and can be fired up to Cone 8 in oxidation.
327 - Great White Stoneware - is a stark white-colored clay, based on our 202 Snow White but with 6% fine sand. 327 glazes beautifully-its crisp white color is a perfect canvas for glazes to show bright, sharp and accurate colors. It's little extra texture makes it ideal for a wider variety of work styles, it's great for slabs and extruding as well as throwing larger forms. Even with its no-grog formula, Great Snow White resists warping and cracking, and alters nicely. It's texture will not interfere with carving, stamping and other surface texture techniques. Great White vitrifies (becomes water-tight) at Cone 6, and can be fired up to Cone 10 in oxidation or reduction.
333 - Black Raven Stoneware - is a clay that has no equal. Black Raven is jet black in color, when fired to Cone 6, and is ideal for dinnerware and other functional pieces. 333 is very user-friendly on the wheel, and handbuilds very well (taking attachments without difficulty). Black Raven textures and alters nicely, it provides a great surface for carving or stamping. 333 vitrifies (becomes water-tight) at Cone 6, and should only be fired to Cone 6 oxidation (never in reduction). We strongly recommend a Cone 04 bisque-firing with the Black Raven Stoneware. Unlike many other "black clays," Black Raven is a true stoneware, and can be used for functional as well as decorative work. When fired properly it can be used in the oven, dishwasher and microwave. It's gorgeous color is not created with stains (so it will not be true black until fired to cone 6), and the Black Raven contains less than 1% Manganese Dioxide.
Stay tuned to learn more about my test results. Thanks for reading and for all your comments.