This kit contains everything you need to dye with indigo crystals (aka pre-reduced or synthetic indigo). Alum is included as a mordant for wool or silk; mordanting is not required for cotton and bast fibers.
2oz Indigo Crystals
4oz Alum (Potassium aluminum sulfate)
4oz Soda Ash (Sodium carbonate)
4oz Thiox (Thiourea dioxide)