Hawthorn Bond 50M Fire Clay

Fire clay is clay that takes very high heat without melting. Ground coarse, it gives a clay body "tooth," a slight grit that helps large pieces stand and dry evenly. Potters use it in stoneware, raku and sculpture bodies. It's an ingredient, not a clay to use straight from the bag, and it's too coarse for glazes.

Use the one your recipe names. Hawthorn Bond 35 Mesh is the coarsest, with the most tooth, for sculpture and raku. Hawthorn Bond 50 Mesh is finer and smoother, for throwing bodies. Cedar Heights 50M Bonding is the same grind as Hawthorn 50 but a different clay. Test before you swap one for another. Mesh counts the openings per inch in a screen; higher is finer.

Usually not. It's one ingredient. Most stoneware bodies mix several clays, such as stoneware clay, fire clay and ball clay, with feldspar and silica, so they throw well, shrink evenly and fire dense. Follow a tested body recipe for your firing temperature.

For shrinkage, roll a slab of the wet clay and scratch a line exactly 10 cm (100 mm) long. Let it dry, fire it, and measure the line again. Each millimeter it lost is 1% shrinkage. For absorption, which tells you how dense the fired clay is, weigh a fired bar, boil it for 5 hours (or soak it for 24), pat it dry and weigh it again. Absorption % = (wet weight − dry weight) ÷ dry weight × 100. Lower numbers mean a denser, stronger clay.

Glaze and clay recipes go by weight, not by volume, and they don't count water. Each ingredient is a share of the dry total. 2% means 2 grams for every 100 grams of dry ingredients. For a 500-gram batch, that's 10 grams. Colors and opacifiers are often listed as extras on top of a recipe that adds up to 100, written like "+2" or "add 2%." Weigh those the same way: 2 grams for every 100 grams of the base recipe. A digital scale that reads to 0.1 gram makes small amounts easy.

A test tile is a small piece of the clay you use, glazed and fired just like your real work. Raw materials vary from bag to bag, and results also change with your clay, how thick you apply the glaze and how your kiln fires. A test tile is the only way to know what you'll get before you glaze a whole batch of pots. Write what's on each tile on the back (an underglaze pencil works), and keep notes so you can repeat what works.

Yes, whenever you handle the dry powder. Fine dust is the main hazard with most raw materials, and some can harm your lungs over time. Wear a NIOSH-approved respirator (N95 or better) while you weigh and mix. A basic dust mask that isn't N95-rated won't protect you. Once a material is mixed with water, dust is much less of a problem, but wipe up spills with a wet sponge before they dry, and mop instead of sweeping. Don't eat or drink while you work, and wash your hands afterward. Check each product's Safety section for anything extra that material needs.