Madder is propagated by planting seed or root division. The plants are harvested in the third year of the plant because the concentration of dye is greater. The harvest takes place at the end of autumn.
The roots are sorted, scrubbed, dried and the bark is stripped from the roots. This bark is crushed into powder. The powder is stored in barrels to age before being sold to the dyers.
Madder contains two colorants: one is red and the second is dark yellowish and soluble in water. To separate them, it is necessary to dissolve the madder powder in water and make it decant. The yellow supernatant water is removed and the operation is repeated until the water runs clear.
Then madder is boiled for several hours and then filtered through a cloth. It is kept liquid.
Another method is to get what is called "madder flower". The roots powder is treated with acidulated water and then rinsed to remove the yellow dyes, mucilages and minerals. The resulting powder has a better dyeing power.
The mordant is generally alum. The use of iron as mordant gives a violet color.
