Patent ID: 8133403

Claim:
A method of etching a surface of a substrate comprising: applying a coating of a color-changing acidic etcher solution to the surface of the substrate, the color changing acidic etcher solution comprising a 0.05 weight % metacresol purple, 2 weight % surfactant, 5 weight % organic solvent, 9.3 weight % hydrochloric acid, and 83.65 weight % water and having a first color at an initial pH below about 7; determining by visual inspection of the color of the surface of the substrate if the coating is substantially evenly dispersed on the surface of the substrate; reacting the color changing acidic etcher solution with the surface of the substrate causing a raising of the pH of the color changing acidic etcher solution towards neutral (pH 7), the color changing acidic etcher solution having a second color at a pH above the initial pH and corresponding substantially to an endpoint of the acidic etcher/substrate reaction; determining by visual inspection of the color of the surface of the substrate if the reaction of the color changing acidic etcher solution is substantially complete; rinsing the color changing acidic etcher solution from the surface of the substrate; and determining by visual inspection of the color of the surface of the substrate if the acidic etcher solution has been substantially removed from the surface of the substrate.