Figure 3-9.  Examples of FAA-approved fabric covering processes.  • A retarder is added to a product to slow drying time.  Used mostly in dope processes and topcoats, a retarder  allow more time for a sprayed coating to flow and  level, resulting in a deeper, glossier finish. It is used  when the working temperature is elevated slightly  above the ideal temperature for a product. It also can  be used to prevent blushing of a dope finish when high  humidity conditions exist. •  An accelerators contains solvents that speed up the  drying time of the product with which it is mixed.  It is typically used when the application working  temperature is below that of the ideal working  temperature. It can also be used for faster drying when  airborne contaminants threaten a coating finish.  •  Rejuvenator, used on dope finishes only, contains  solvents that soften coatings and allow them to flow  slightly. Rejuvenator also contains fresh plasticizers  that mix into the original coatings. This increases the  overall flexibility and life of the coatings.  •  Fungicide and mildewicide additives are important  for organic fabric covered aircraft because fabrics,  such as cotton and linen, are hosts for fungus and  mildew. Since fungus and mildew are not concerns  when using polyester fabric, these additives are not  required. Modern coating formulas contain premixed  anti-fungal agents, providing sufficient insurance  against the problem of fungus or mildew. The covering processes that utilize polyester fabric are the  primary focus of this chapter. Examples of FAA-approved  aircraft covering processes are listed in  Figure 3-9 . The  processes can be distinguished by the chemical nature of the  glue and coatings that are used. A dope-based covering process  has been refined out of the cotton fabric era, with excellent  results on polyester fabric. In particular, plasticizers added to  the nitrate dope and butyrate dopes minimize the shrinking and  tautening effects of the dope, establish flexibility, and allow  esthetically pleasing tinted butyrate dope finishes that last  indefinitely. Durable polyurethane-based processes integrate  well with durable polyurethane topcoat finishes. Vinyl is the  key ingredient in the popular Poly-Fiber covering system. Air  Tech uses an acetone thinned polyurethane compatible system. Available Covering Processes 3-8 Aircraft Covering Systems Covering System PFU 1020 PFU 1030 PFUW 1050 Nitrate Dope Poly-brush EkoFill Dacproofer SF6500 PFU 1020 PFU 1030 PFUW 1050 Rand-O-Fill Poly-spray EkoFIll SrayFil SF6500 CHSM Color  Coat Colored  Butyrate Dope Ranthane  Polyurethane Vinyl Poly-tone, Aero-Thane, or  Ranthane Polyurethane EkoPoly Tinted Butyrate  Dope Superflite™  CAB STC # Allowable Fabrics Base Filler Cement UV Block Topcoats UA-55 New Super  Seam Poly-tak EkoBond U-500 U-500 Urethane Water Dope Vinyl Water-borne Dope Urethane Ceconite™  Poly-Fiber™  Superflite™ Ceconite™ Poly-Fiber™ Ceconite™  Poly-Fiber™ Superflite™  101,102 Superflite™  101,102 SA7965SW SA4503NM SA1008WE SA01734SE SA00478CH and others Air-Tech Ceconite™/ Randolph System Stits/Poly-Fiber™ Stewart System Superflite™ • System1 • System VI APPROVED PROPRIETARY PRODUCT NAME