madder is one of the oldest known dyestuffs and has been used to create tones of red, orange and yellow for thousands of years. the pigment is obtained from the root, which is red in colour when pulled from the ground.
chalk and alum are used commonly as mordants for madder and do not alter the colour but make it more wash and lightfast.
the t shirt shown below was dyed using 50g chopped madder root and 1/2 tsp of alum and 1/2 tsp of chalk. the resultant colour was a mid washy pink. but boiling/cooling the dyebath for longer results in colour changes.
after doing this t shirt i purposefully burnt the remaining madder root in the bath and put in a sample of organic bamboo jersey to see what colour was made. a deep rich golden brown colour was produced.