Cleaning efficacy was measured using a custom-built reciprocating scrub machine. To measure chemical cleaning,the scrub machine was modified to minimize both mechanical and thermal energies.
Soiled panels were scrubbed with a sponge wetted with neutral-pH cleaning formulations containing 2% levels of various solvents. Once the first formulation completely removed the soil from the panel, the scrub machine was stopped and results were photographed and analyzed.
To effectively quantify cleaning performance, completed scrub test panels were scanned into a computer using a standard flatbed scanner. The scanned images were then analyzed to evaluate the cleaning performance of each formulation using grayscale measurements of remaining soil.