What are the uses of potash …

Fire Retardant: The use of potassium alum for textiles, wood and paperless flame resistance is as fire-retardant.

Tanning: For leather tanning, potassium alum is used to extract moisture from the hide and avoid rotting. Alum is not covered and can be washed out, as compared to tannic acid.

Iron and Steel Dissolving: This aluminium solution has the property that steels are dissolved without affecting aluminium or base metals. For machined castings of steel parts of machinery, alum solutions can be used.

Gourmet Food: Potassium alum may be an acidic component in baking powder to provide a second leavening step at high temperatures (although sodium alum is more widely used for this purpose). Bakers in England made bread whiter with alum during the 1800s.

Used for Dyeing: Alum was used to form a permanent link between natural textile fibres like wool and dye, as mordant.