Optimized in-line mask cleaning system

A method for cleaning a mask having a front and a back surface and a plurality of side edges, one of said side edges being a top side edge and another side edge being a bottom side edge, the method comprising:

• a) supporting the mask vertically such that said top side edge is an uppermost side edge;
• b) simultaneously spraying with an aqueous alkaline cleaning solution both the front and the back surface of the mask by directing balanced front and back streams of said alkaline solution to impinge on the front and back surface of the mask respectively at an angle of between about 40.degree. and about 50.degree. and at a pressure of between about 150 and 500 psi, beginning at one edge of the mask and ending at an opposite edge;
• c) removing any residual cleaning solution from the mask by traversing a set of a front and a back air-knife beginning at one edge of the mask and ending at an opposite edge, wherein the front and back air-knives apply two balanced gaseous streams simultaneously to both the front and the back surfaces of the mask at a pressure sufficient to blow said cleaning solution off the mask surface.