Permanent Yellow is a favorite label for zinc yellow or zinc chromate in oil, although baryta yellow or strontia yellow is also considered permanent. Zinc yellow when it first appeared upon the American market was held very high in price, and was therefore rather rarely found in the list of oil colors, but more on the artists' color and coach color lists. It is still anywhere from 25 to 35 per cent higher in cost in the dry state than lemon chrome yellow. The color grinder will test zinc yellow for clearness of tone, softness of texture and tinting power although it is seldom, if ever, used for the latter purpose. A fine quality of zinc yellow must not be harsh when rubbed up in oil with the spatula, as that would show that it is liable, after grinding in oil and put up for the market in containers, to become grainy. Pure zinc yellow will require anywhere from twenty-two to twenty-four parts by weight of bleached or clarified linseed oil to from seventy-six to seventy-eight parts by weight of the pigment, which must be bone dry, as moisture will prevent the production of smooth paste. Modern scientific research has discovered that pure zinc chromate ground fine in linseed oil and reduced to brushing consistency with linseed oil and pure turpentine drier prevents, when applied to rust-free iron or steel, the formation of rust or corrosion through galvanic action or atmospheric influence.