Photograph of copy of label, Blackor Co., Southern California, 1929. "Blackor, The Super Hard-facing Product (Patented), Supreme, Abrasive-resistant material for Oil & Mining Industries, Agricultural Implements, Etc., Directions For Using: A layer of Blackor about 1/4 inch thick is placed on the surface to be hardfaced, which has been cleaned and prepared as for ordinary welding. A ground surface is preferable but not absolutely necessary. A copper plate is used alongside edges. Blackor is melted with the electric arc: a fine-pointed carbon pencil, with from 150 to 250 amperes at 50 to 80 volts should be used for ordinary work. As soon as the Blackor has been melted, remove arc and add another layer of Blackor. Use only enough heat to melt: mixing with the underlying metal should be avoided as much as possible. Three or more layers of Blackor should be used in order that the outer layers should pick up less of base metal. Where very hard metal is desired the number of layers should be increased. Where softer metal is satisfactory fewer layers are necessary. It is to be remembered that even the softest Blackor (that is very few thin layers) is harder than and will wear better than so-called hard-facing metals, while Blackor put on following directions for maximum hardiness compares with the hardest metal inserts and has the great advantage of not 'cutting between.', Patent 1613942, Protected by American Patent Protection Corporation, Other Patents Pending, Net Weight [ilg] Pounds, Blackor Company, 215 West 7th St. Los Angeles, Calif." -- label.