Mordanting is a treatment to which fibers and fabrics are subjected before dyeing, which prepares them for the absorption of the color and facilitates its fixing. It was carried out by immersing the fibers or fabrics in baths containing mordant substances, such as vinegar and salt, tannins or rock alum (hydrated aluminum and potassium sulfate). The immersion in these baths began cold, then everything was brought to the boil. The treatment lasted about an hour and a half.