Plexiglas Turning Milky
I recently purchased a T-28 Trojan canopy and noticed that the Plexiglas was starting to turn a bit "milky".
Is there anything I can use to cleared it up (treatments, solvents, etc.) ?
I've removed light crazing from aircraft plexiglas windows over the years using a variety of methods. These include: 1). micro mesh polishing kit (which is really more for scratches but works on crazing too) 2). plexiglas polish (see an aircraft supply catalog like wag, wicks, spruce) 3). car polish including rubbing compound. On my car headlight plexi I've used a lens restorer compound with success. Before any polishing be sure to remove all dust and dirt from the window using soap, water, and a CLEAN towel. Once the plexi is restored keeping a good coat of spray furniture wax (aka pledge) will help keep the windows from crazing.
I have used the Micro Mesh kit to restore a scratched up windshield. But for what you are describing, I would use Novus #2 polish followed by some #1. They also make a #3 polish, which has a more coarse grit of polish. I used an electric buffer from Harbor Freight with the adjustable speed. I threw away the cheap terry cloth buffer pad that came with it and bought a professional grade wool buffing pad. The #2 polish removed the milky look after about the 2nd or 3rd pass. Afterward I went over it a couple of times with the #1 polish just to insure a good optical quality. I bought the polish at a local place that sells a lot of Lexan and Plexiglas, but I have seen it advertised in aircraft supply houses. Like any other polish, you want to use it in the shade and buff it off before it dries out.
The Novus products can be found at a lot of local retail locations like Harley shops. The products (#1 and#2) do work very well. But like any polishes, they will only remove surface haze. Older plexi can go milky all the way through, probably (?) because of long term sun exposure. There isn't much you can do about that other than replace the plexi.
The fact that it's 40+ yrs old and probably been exposed to sunlight all it's life would suggest that short of melting it down and starting over, it's well past it's useful life. Certainly wouldn't hurt to work a section and see how clean you can get it. BTW, you don't need anything fancy, wet sand it out with a few drops of liquid soap in water and 3m wet or dry sandpaper. Start with 1000 grit and work up to 6000.