1 - A silvery grey metal for etching. It is as little as a quarter of the price of copper depending on world markets, and therefore commonly used. Experienced printmakers, however prefer the ‘cleaner’ line produced by the copper plate.
2 - A pure but relatively transparent white pigment mostly used in watercolors and gouaches, with a small usage in oil paint.
3 - A yellow pigment now obsolete, but the lightest shades of Cadmium Yellow have a significant proportion of Zinc incorporated with the Cadmium. This is not regarded as an impurity in the same way that Selenium is not considered an impurity in Cadmium Red. In both cases they are the result of the chemical production of that shade of yellow or red. Cadmium and Zinc are very similar chemically and readily combine chemically like this.