A painting system comprises a pressurized paint canister and a pressure fed paint brush or powered paint roller connectable to the pressurized paint canister. A process for removing ionic impurities from a photoresist solution is also provided which comprises passing the photoresist solution through said filter sheet to remove ionic impurities therefrom. Particular aspects of the present invention are described in the claims, specification and drawings. The second reflectance spectrum is analyzed using the diffuse reflection property so as to determine a characteristic of the surface layer of the sample.