Skip to Main Content »

How to Repair Scratched Plexiglass with 303 Aerospace Protectant


Download pdf instructions 99k

Cut Polishing & Finishing
(For clear plastics: Lexan®, acrylics,
polycarbonates, clear coat and also glass)


  • A Variable Speed Rotary Polisher
  • 3M5701 - Wool buffing pads for plastic (foam pads for clear coat)
  • 3M5710 - Double sided pad adaptor
  • 3M5954 - Super Duty Compound ? qt (or micro-fine for clear coat)

*Or equivalent.

I Preparation:

Compounding (aka cut-polishing) is a safe and effective way of preparing surfaces before finishing with 303 Aerospace Protectant (303). Compounding simply, quickly and easily removes oxidation and all but the deepest scratches for that `perfect finish' when finished off with 303 Aerospace Protectant (303). Proper cut-polishing leaves the surface smooth and will even remove blemishes and scuff marks that otherwise remain forever. 

A skilled operator can use this method to remove scratches, oxidation and haze from Lexan®, acrylic and polycarbonate windows; motorcycle and fireman helmet visors; the clear vinyl windows in boat enclosures, soft tops and convertible tops; acrylic spas and showers; the plastic covering headlights and tail-lights; and residential and automobile glass - windows, windshield, mirrors. 

In all cases, after cut-polishing apply 303 to complete the job & perfect the finish. Though there may be the slightest of swirl marks left after compounding or cut-polishing, finishing with 303 causes them to completely disappear to leave a perfect, no-swirl finish repellent finish on acrylic and gelcoat, and a fully restored, "like-new clarity again on acrylic, Lexan®, other clear plastics, clear vinyl and glass.

Apply line of cutting compound to the wool pad. With buffer set very low so it doesn't "spin off" the cutting compound, use a low RPM to first spread the compound on the area. After spreading, bring the RPM up to speed(1800) and sweep back and forth polishing out the scratches/oxidation. IMPORTANT: Low RPM and light pressure are the key! An unpracticed operator can burn a surface by holding the buffer too long in one position. Always use buffer in a Continuous, sweeping motion. It takes very little pressure or time to completely prep a surface.

Periodically clean the wool pad to remove any excess compound. Compound builds up and can clot in the wool. It is easily cleaned by holding the polisher at your side with the pad facing out and running the "spur" tool from the center of the wool pad to the edge while the pad is spinning. Do this regularly during compounding.

After compounding the area, merely turn over the reversible pad (or using a clean pad), spray 303 directly on the polished surface and polish it in at 1800 RMP until surface is completely dry. Note: After compounding it is not necessary to remove any residue. Proceed directly to: II Application. 

II Application:

The keys to applying 303 are 1) low RPM and 2) light pressure and 3) keeping the buffer moving. Set the variable speed buffer to 1800 RPM max. Using the trigger on the variable speed buffer the operator can vary the RPM from 0 to 1800 RPM. 

Apply 303 in the shade or indoors, a surface that is NOT hot to the touch. 

Do 2-10 square feet at a time. Mist 303 lightly on surface or apply with a sponge. Spread evenly at low RPM with wool or foam pad, then immediately buff in at higher RPM (1800 max) and polish until completely dry...a matter of seconds. Repeat over entire surface. Application time for an experienced applicator on a typical spa or shower, for example, should take no longer than 1-3 minutes. 

303 Aerospace Protectant is NOT left to dry to a haze. It is applied and immediately spread, buffed in and polished. Use sufficient product so that when spreading 303 with the buffer it wets the area to be polished.

Buff in and polish until surface is COMPLETELY dry. A proper finish has a lustrous, velvety look and feel. Any moisture or dampness left on the surface after buffing indicates an improper application caused by either a) using too 
much product or b) a damp buffing pad. 

Changing pads: Pads should be changed if they become damp and no longer able to completely dry the treated surface. Used wool pads may be washed in the washing machine and reused.

When a wool pad is new, small fibers pull loose and can remain. These are easily removed with an air hose or by dusting off with a towel or cloth. Or if any excess product remains, remove fibers and excess product by washing with water and drying.

III Application :

Gelcoat Fiberglass: Used in the above procedure, 303 Aerospace Protectant is a quick and efficient way to restore faded, gelcoat fiberglass (polyester resin) to a "like-new" color and gloss. 

Because of the absorbency of gelcoat fiberglass, it is sometimes necessary to apply more 303 on this surface than clear plastic or glass. 

Prior to applying 303 to badly oxidized gelcoat, it is best to prep the surface using the procedure described in Section I.

Recommendation on all larger areas: After finishing any large area (vehicle, boat, RV) wash the treated surface(s) with water and then dry with a soft, clean, dry cloth or towel to remove any excess product. 

©1991 303 Products, Inc.