By the indigo process of dyeing canvas, a reduced bath is made as follows. Take 10 gal. of water and add 5 oz. of finely powdered indigo, 144 oz. of dry slaked lime, and 9 1/2 oz. of copperas; stir the bath and keep it covered, stirring afterwards from time to time till the blue of the indigo disappears. Steep the canvas in this for two hours, then remove and hang up in the open air to oxidise. If the cauvas is not sufficiently blue after exposure, repeat the dyeing process. Pass through a tint;: of dilute sulphuric acid (1 part acid to 20 parts water), and then wash thoroughly in clean water, without soap.