saturated with water. Remove small pieces of remaining paper  with masking tape. Paper decals can be removed by rubbing the decal with a cloth  dampened with lacquer thinner. If the decals are applied over  painted or doped surfaces, use lacquer thinner sparingly to  prevent removing the paint or dope. Remove metal decals by moistening the edge of the foil with  aliphatic naphtha and peeling the decal from the adhering  surface. Work in a well-ventilated area. Vinyl film decals are removed by placing a cloth saturated  with MEK on the decal and scraping with a plastic scraper.  Remove the remaining adhesive by wiping with a cloth  dampened with a dry-cleaning solvent. The use of several different types of paint, coupled with  several proprietary coatings, makes repair of damaged and  deteriorated areas particularly difficult. Paint finishes are not  necessarily compatible with each other. The following general  rules for coating compatibility are included for information  and are not necessarily listed in order of importance: Any of the finishes may be present at any given time, and  repairs may have been made using material from several  different type coatings. Some detailed information for  the identification of each finish is necessary to ensure  the topcoat application does not react adversely with the  undercoat. A simple test can be used to confirm the nature  of the coatings present.  The following procedure aids in identification of the paint  finish. Apply a coating of engine oil (MIL SPEC, MIL- PRF-7808, turbine oil, or equivalent) to a small area of the  surface to be checked. Old nitrocellulose finishes soften  within a period of a few minutes. Acrylic and epoxy finishes  show no effects. If still not identified, wipe a small area of the surface in  question with a rag wet with MEK. The MEK picks up  the pigment from an acrylic finish, but has no effect on an  epoxy coating. Just wipe the surface, and do not rub. Heavy  rubbing picks up even epoxy pigment from coatings that are  not thoroughly cured. Do not use MEK on nitrocellulose  finishes.  Figure 8-22  provides a solvent test to identify the  coating on an aircraft. Paint touchup may be required on an aircraft following  repair to the surface substrate. Touchup may also be used to  cover minor topcoat damage, such as scratches, abrasions,  permanent stains, and fading of the trim colors. One of the  first steps is to identify the paint that needs to be touched up.  Existing finishes on current aircraft may be any one of several  types, a combination of two or more types, or combinations  of general finishes with special proprietary coatings. 1.  Place vinyl film, adhesive side up, on a clean porous  surface, such as wood or blotter paper. 2.  Apply recommended activator to the adhesive in firm,  even strokes to the adhesive side of decal. 3.  Position the decal in the proper location, while  adhesive is still tacky, with only one edge contacting  the prepared surface. 4.  Work a roller across the decal with overlapping strokes  until all air bubbles are removed. 5.  Epoxy topcoats adhere to any paint system that is in  good condition, and may be used for general touchup,  including touchup of defects in baked enamel coatings. 6.  Old wash primer coats may be overcoated directly with  epoxy finishes. A new second coat of wash primer  must be applied if an acrylic finish is to be applied. 7.  Old acrylic finishes may be refinished with new  acrylic if the old coating is softened using acrylic  nitrocellulose thinner before touchup. 8.  Damage to epoxy finishes can best be repaired by  using more epoxy, since neither of the lacquer finishes  stick to the epoxy surface. In some instances, air- drying enamels may be used for touchup of epoxy  coatings if edges of damaged areas are abraded with  fine sandpaper.  1.  Old type zinc chromate primer may be used directly for  touchup of bare metal surfaces and for use on interior  finishes. It may be overcoated with wash primers if it  is in good condition. Acrylic lacquer finishes do not  adhere to this material. 2.  Modified zinc chromate primer does not adhere  satisfactorily to bare metal. It must never be used over  a dried film of acrylic nitrocellulose lacquer. 3.  Nitrocellulose coatings adhere to acrylic finishes, but  the reverse is not true. Acrylic nitrocellulose lacquers  may not be used over old nitrocellulose finishes. 4.  Acrylic nitrocellulose lacquers adhere poorly to bare  metal and both nitrocellulose and epoxy finishes. For  best results, the lacquers must be applied over fresh,  successive coatings of wash primer and modified zinc  chromate. They also adhere to freshly applied epoxy  coatings (dried less than 6 hours). 8-19 Paint System Compatibility Identification of Paint Finishes Paint Touchup Removal of Decals 