Armour etch is a fast acting specially formulated glass etching compound that lets you create permanent etched designs on windows, mirrors and household glassware.create your own custom glass etching stencil or use one of our pre-cut stencils.this unique glass etching system enables anyone to personalize and decorate glass or mirrors in minutes with no previous experience.try it, you’ll love it! Not intended for use by children. Will not etch plastics or some pyrex.