Cream of Tartar (Potassium Bitartrate) – Dyeing Assistant (with Alum)

Cream of tartar (potassium bitartrate) is a traditional dyeing assistant used together with alum when mordanting—especially on wool and silk. It helps the mordant bath stay gently acidic, supports more even uptake, can help keep protein fibres feeling softer, and is often used to brighten / clarify certain shades (especially some reds).

Cream of tartar works best with protein fibres (wool & silk) and is seldom used with cellulose fibres (cotton/linen). It is typically used alongside alum:

Alum (Aluminium Potassium Sulphate)

Use rate (starting point): 5–6% WOF (Weight Of Fibre).

For protein fibres, a practical mordanting starting point is 10–15% alum (WOF), then add 5–6% cream of tartar (WOF) after alum is fully dissolved.

Quick use: Dissolve alum completely in hot water, add cream of tartar and stir until dissolved, then add fibres and heat gently (avoid boiling). Allow fibres to cool in the bath for more even uptake.

New to cream of tartar? See our step-by-step guide (dosage + best pairings).

Notes: Cream of tartar is an assistant, not a stand-alone mordant. Results vary with fibre type, water chemistry, dye material, and process. Avoid inhaling fine powder; store sealed in a cool, dry place. SDS is available upon request.