Indigo powder can be used as a natural colouring agent in soaps. It makes it possible to obtain magnificent blues ranging from blue-grey to light blue to dark blue. It is usually dosed between 1/2 and 1 1/2 teaspoon for 500 g of oils. For a more intense blue, the powder is dissolved in the water-hydroxide mixture. For a lighter blue, the powder is dissolved in a little oil before adding it to the trace. Attention: the colour varies according to the oils and butters used.