REMASKING

The masking paper used on Vical acrylic sheet will retack and may be replaced if desired. The adhesive bonds firmly to itself, however, so the coated sides of the masking paper must not be allowed to contact each other. The masking paper can be rolled up in loose tubes and stored on pegs in a clean, dry area. Take care to avoid contaminating the masking paper with dirt to keep from scratching the Vical acrylic when the masking paper is re­applied.

Prepared masking papers are available from a number of sources and may be used for remasking. Before using a different masking paper, however, check the adhesive to be sure it will not attack the Vical acrylic.

PROTECTIVE COATINGS

Masking compounds that can be sprayed on the Vical acrylic and later peeled off may be used, especially when formed parts are to be masked.

The spray masking compounds should not have a harmful chemical action on the Vical acrylic. Some masking compounds may be used indoors for periods as long as 12 months. In general, no masking compound should be used on parts that will be stored outdoors for more than two months.

When spray masking compounds are used, the coating must be at least 3­5 mils thick. The film should also be uniform and free from runs and other imperfections. If the film is too thin, it may be difficult to remove.

To remove spray masking from Vical acrylic, 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 thin, apply a fresh coating of the masking compound, let it dry, then remove it. In some pallets, it might be necessary to apply a layer of cheesecloth over the fresh spray coating, let the coating dry, and then apply another coating and let it dry before attempting removal. The cheesecloth reinforces the spray coating and makes it easier to remove. If the film has deteriorated because it has been stored outdoors, soaking the coated part in cold water for 24 to 48 hours may help to soften the film. Stripping compounds supplied by the manufacturers of the spray masking compounds may also be used if they will not craze the Vical acrylic.

Protective spray masking coatings must be removed from parts made of Vical acrylic before the parts are annealed. If the coatings are not removed before annealing, optical distortions may appear in the annealed part in areas in which the thickness or surface of the coating is irregular.

Acrylic Sheet General Information