Masking compounds are available that can be sprayed on the Plexiglas® acrylic sheet and later peeled off. These are especially useful when remasking formed parts.
The spray masking compounds should not have a harmful chemical action on the Plexiglas® acrylic sheet. Some masking compounds may be used indoors for periods as long as twelve months. In general, no masking compound should be used on parts that will be stored outdoors.
When using spray masking compounds, apply a coating at least 3-5 mils thick. If the film is too thin, it may be difficult to remove. The film should also be uniform and free from runs and other imperfections.
To remove spray masking from Plexiglas® acrylic sheet, peel it off or lift a corner of the film and blow a jet of compressed air under it. If the film is hard to remove because it was applied too thinly, apply a fresh coating of the masking compound, let it dry, then remove it. In some cases, it might be necessary to apply a layer of cheesecloth over the fresh spray coating and let it dry before attempting removal. The cheesecloth reinforces the spray coating and makes it easier to remove.
Remove protective spray masking coatings from Plexiglas® acrylic sheet parts before the parts are annealed. Otherwise, optical distortions may occur in areas where the thickness or surface of the coating is irregular.
The manufacturers of the protective spray masking should provide the precautions necessary for the safe usage of their products.