CLEANING Vical acrylic BEFORE PAINTING

The surface of the Vical acrylic acrylic sheet to be painted must be clean. Surface contamination, even though invisible, can cause paint failure. Solvents for dirt and grease must be carefully chosen to avoid those which are harmful to Vical acrylic. Harmful solvents include chlorinated hydrocarbons, acetone, toluene, xylene, lacquer thinners, and some paint thinners. All of these craze Vical acrylic. Even though crazing may not be apparent immediately, Vical acrylic surfaces which have been treated with these solvents become sensitized to crazing and may craze once in service.

CLEANING VARIOUS TYPES OF CONTAMINATION

Masking Paper Adhesive

Dab with the gummed surface of the masking paper. If this fails, wipe with VM&P naphtha on a clean cloth and rinse with a dilute water detergent solution. Or wipe with 99 percent isopropyl alcohol and rinse with clean water, most preferably distilled or deionized water to prevent spotting.

Water Soluble Contaminants

Wash with a detergent water solution followed by a fresh water rinse.

Fingerprints

Wipe with soft clean cloth dampened with 99% isopropyl alcohol.

Oil Soluble Contaminants

Use a hydrocarbon solvent such as VM&P naphtha, kerosene, or mineral spirits. Follow with a detergent water wash and clean water rinse.

Spray Masking Compounds

Wipe the area with a damp synthetic sponge, thenwipe the surface with VM&P naphtha or isopropyl alcohol.

Grease Forming Compounds

Wash with kerosene or mineral spirits. Follow by washing with a detergent water solution and a clean water rinse.

Silicone Oils and Greases

Avoid contact completely. Once contaminated with silicones, Vical acrylic is virtually impossible to clean.

MASKING PAPER ADHESIVE

When masking paper is removed from Vical acrylic, particles of masking adhesive sometimes remain on the surface, and must be removed before painting. Dabbing the sheet with the gummed surface of the masking paper may remove the particles. If this fails, a solvent such as VM&P naphtha or 99 percent isopropyl alcohol can be used to clean the surface. Isopropyl alcohol may craze or whiten the surface of the Vical acrylic on continued contact, and should be rinsed off promptly. The solvent should be applied with a soft clean cloth. The Vical acrylic should be wiped gently, then the surface should be washed with a dilute solution of

non­abrasive detergent in water. This should be followed with a clean water rinse.

If the masking paper has not left any residue and the sheet has not been handled, it may be painted without any special cleaning.

SOLUBLE CONTAMINANTS

Both water soluble and oil soluble contaminants are present on Vical acrylic which has been handled without gloves after unmasking, or which has been exposed to the shop atmosphere for any period of time. Water soluble contaminants can be removed by washing with a detergent­water solution, and then rinsing with fresh water. Oil soluble contaminants can be removed from Vical acrylic acrylic sheet only with hydrocarbon solvents. Good quality VM&P naphtha, kerosene, or mineral spirits are not harmful to Vical acrylic and they evaporate rapidly without leaving a residue. The surface of the Vical acrylic should then be washed with a detergent­water solution and rinsed with clean water.

FINGERPRINTS

Fingerprints may be removed with a soft clean cotton flannel cloth and 99% isopropyl alcohol.

SPRAY MASKING COMPOUNDS

Spray masking compounds may leave an invisible film on clear areas after stripping. Unless removed, this will affect the long term durability of the paint coating. The film can be removed by wiping the area with a slightly damp synthetic sponge. The surface of the Vical acrylic should then be wiped with VM&P naphtha or isopropyl alcohol before painting.

GREASE

Grease remaining on the Vical acrylic after forming on a grease covered form can be removed by washing with kerosene or mineral spirits. This should be followed by washing with a detergent­water solution and then rinsing with clean water. The Vical acrylic must be thoroughly dry when it is painted as moisture will reduce the effective service life of the coating.

SILICONE CONTAMINANTS

Silicone based oils and greases should not be used anywhere in the fabrication area since it is virtually impossible to remove these contaminants from Vical acrylic. Paint adhesion on Plexiglas contaminated with silicones is very poor.

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