Chrome Oxide

Add half a gram of chrome oxide to every 100 grams of a dry clear or white base glaze (0.5%), using a base glaze without zinc. Make test tiles at 0.5%, 1% and 2%. Chrome gives an opaque grass or olive green, not the glossy, see-through greens of copper.

Zinc. Chrome and zinc together give browns. Check your base glaze recipe for zinc oxide, and switch to a zinc-free base if you want green.

Chrome can turn to vapor in the kiln and react with tin oxide in other glazes, even on a different pot. That leaves pink blushes on tin whites. Keep chrome-glazed pieces away from tin glazes in the kiln, or fire them in separate loads.

Chrome greens are opaque and earthy, and they change less with the kiln atmosphere than copper does. Too much chrome makes a glaze dry and dull. Copper greens are brighter and can be glossy and see-through, but copper makes glazes runnier. Many potters use chrome for solid greens and copper carbonate for glossy ones.

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.