With the advent of high energy deposition technologies, thin film coatings are generally more robust than they were even twenty years ago. However, thin film coatings are extremely thin and depending on the type, vary in hardness. Therefore, care should be used in handling and cleaning coated optics. Newport Thin Film Laboratory suggests the following cleaning methods for cleaning thin film coatings on glass and metal substrates:
Solvents: Organic solvents such as isopropyl alcohol, ethanol, methanol and acetone are safe to use, as is distilled water. Do not use acids, bases, ammonia or industrial or household cleaners.
Wipers: Only soft, clean cotton, wet with a suitable solvent should be used. Tissues and some types of lab wipes that are composed of wood fibers will scratch thin film coatings. Soft camel hair or other suitable synthetic brushes can be used to remove dust.
Technique: Blow dust off of surface before wiping the surface. A soft brush can be employed. Wipe the surface gently with even strokes. Do not buff the surface.