Very flexible and durable compositions are made in various colors by grinding chemically pure pigments of great color strength in castor oil to fairly stiff paste form, which are let down with celluloid varnish for use on canvas covered packages. These are mostly used for the transportation of powder and other explosives, the color denoting contents of the packages to the initiated. It has been ascertained, that when gun cotton in solution with amylacetate has a certain small percentage of castor oil added, the resulting film, when dry shows a toughness nearly three times greater, than does the film of the straight solution. Pigments such as Prussian blue, chemically pure chrome greens, chrome yellows, toluidine red are mostly in favor and may be ground fine in castor oil in about the same proportion as if linseed oil were used. The proportion of paste color and celluloid varnish varies according to the nature of the protection desired, and the bulk of the paste. So for instance 4 oz. of Prussian blue will color one gallon of varnish, while from 6 to 8 oz. of dark chrome green and from 8 to 12 oz. of chrome yellow and 8 oz. of toluidine red are required.