English Grolleg Kaolin

Thin walls, a very white, low-iron clay, and a body that melts partly to glass at full temperature. Grolleg carries a little natural flux, which helps. Fire to the body's full temperature, because underfired porcelain stays opaque.

Kaolin on its own is "short": it cracks instead of stretching. Add 1 to 3% bentonite or Veegum to the dry mix and test. Ball clay also adds stretch, but it makes porcelain less white.

Both are clays. Kaolin, also known as china clay, is purer and fires whiter, but it isn't very plastic on its own: a coil of it cracks when you bend it. Ball clay is finer and stickier, so it adds plasticity (how far wet clay bends before it cracks) and strength, but it fires a little darker and shrinks more. Porcelain is mostly kaolin, with a little ball clay or bentonite added so it can be thrown.

If your recipe names one, buy that one. Starting from scratch:

For glazes and everyday white bodies: Treviscoe, Remblend or Standard Porcelain.

For translucent porcelain: English Grolleg or New Zealand Halloysite, the whitest.

For slip casting: optiKasT.

For more stretch in a throwing body: #6 Tile Clay.

To stop a high-kaolin glaze from cracking as it dries: Burgess Iceberg Calcined Kaolin.

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.