The masking paper used on Plexiglas® acrylic sheet is not water repellent. If masked Plexiglas® acrylic sheet is soaked with water, a white residue may be left on the material when the masking paper is removed. To avoid this, store masked sheet where it cannot come into contact with water. If a residue is deposited on the Plexiglas® acrylic sheet, it may be removed by wiping the surface gently with a clean, soft, damp cloth and drying it with a soft flannel cloth.
Plexiglas® acrylic sheet can be unmasked by lifting the masking paper along one edge and rolling it around a dowel or cardboard tube. The paper may be built up on the dowel or tube in successive layers using the adhesive layer to secure the turned up edge of the masking to the paper-covered dowel. Remove all residual adhesive from the sheet surface at the time of masking removal. Any residue that remains can be cleaned off by wiping with a soft clean cloth dampened with isopropyl alcohol.
Unmasking usually builds an electrostatic charge on the Plexiglas® acrylic sheet. The electrostatic charge attracts dust and lint to the acrylic surface. Eliminate the charge by wiping the sheet with a dampened cloth after unmasking. During dry weather, wet down the shop floor occasionally to minimize dust.
For operations such as a strip heating, cementing, or applying glazing sealants, only the masking paper in the area being worked on should be removed from the sheet. When cutting out small sections of masking paper, take care not to score or scratch the Plexiglas® acrylic sheet surface underneath. Scoring the sheet may reduce its impact resistance.
Special tools can be employed to minimize the possibility of scoring or scratching the Plexiglas® acrylic sheet when removing small masking sections (contact Altuglas International for information on commercial tools and materials for Plexiglas® acrylic sheet). When used properly in combination with a suitable solvent, these tools will not score or scratch the sheet.
Masking paper may be difficult to remove in the following circumstances: 1) Plexiglas® acrylic sheet that has been stored outdoors and exposed to sun and moisture; and 2) sheet has been stored indoors for lengthy periods or has been exposed to heat or high humidity. When the sheet will be thermoformed, and the masking paper is not adhering too tightly, flash heating the sheet for 60 seconds at 350°F will loosen the paper enough for easy stripping.
In cases where the paper is sticking more tenaciously, it may be necessary to choose a more aggressive solvent to loosen the masking paper. In such cases, thoroughly soak the masking paper with the solvent, and allow at least 10 minutes for the solvent to penetrate the paper. Strip as described above. If necessary, apply more solvent along the separation line between the masking paper and the Plexiglas® acrylic sheet.
Use only solvents that will not attack the Plexiglas® acrylic sheet. A list of recommended solvents for removing masking paper is available from Altuglas International. Remove the solvent from the Plexiglas® acrylic sheet as soon as possible by first washing the sheet with isopropyl alcohol, then with soap and water and, finally, with clear water.
Before attempting to remove tightly adhering masking with solvents, become familiar with the properties of the appropriate solvents and take proper safety precautions. Obtain Material Safety Data Sheets from the manufacturer. Ventilate the work areas as OSHA requires, and prohibit smoking or open flame.
Unmasked pieces of Plexiglas® acrylic sheet should be stored in the original shipping cases. Full cases can be stored on edge. Open cases can be stored flat or they can be placed on edge in roller-type racks. Uncased sheets may be stored in A-frame racks. The interleaving tissues should not be removed until the sheets are used.
The masking paper used on Plexiglas® acrylic sheet will regain its tack 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 Plexiglas® acrylic sheet when the masking paper is reapplied.
Prepared masking papers are available from a number of sources and may be used for remasking. Before using one of these products, however, check its adhesive to be sure it will not attack the Plexiglas® acrylic sheet.