Potassium Carbonate is a strong alkaline salt, which assists with the break down of the cellulose within the dried Persicaria tinctoria / Indigo Leaf in the Dried Leaf Vat recipe. It will eliminate some of the calcium deposit from the Lime,( Calcium Hydroxide) within the vat to a certain degree.
Potassium Carbonate is an ingredient found in many household cleaning products, and breaks down, calcium deposits from hard water, fats or grease.
A strong alkaline, therefore gloves are required when handling and dyeing. A known irritant. Please take all necessary precautions, googles, apron, gloves and mask.