Gray Etch Primer 12 Oz Aerosol - Liquid Print Hydrographics Paint Supplies Hydrographics 12 Oz Aerosol Gray Etch Primer Direct to metal primer for use with all of our basecoats. Convenient 12 ounce aerosol for easy use. Multi-Directional Spray Nozzle. This product was specially forumlated for the unique demands of the hydrographics industry.