On Monday, May 25, 2015 at 9:00:05 AM UTC-6, firsys wrote:
For year, I used to use mirrorglaze for my canopy,
almost every preflight.

Then it disappeared from local plastics supply.

Bought some online a year or two ago, used with good
results.
Yesterday, I squirted some on the PIK canopy and immediately
started polishing.
To my dismay some patches seemed to polimnerise
and form a hard patch. Continued polishing with
a clean cloth removed some; A water flush did some good
but I was left with a few patches, right in the vsion line,
which did not yield.
Anyone know if there is a benign solvent which will remove these?

John firth

I suspect what you used is Mcguire's #10 (grey bottle) "Mirrorglaze" which is an excellent if dated canopy polish. (Developed by the USAAF in WWII) It's still my favorite but it does take more work to remove if allow to day. The principle of operation is that it's a hard, clear wax whose refractive index is the same as Plexiglass therefore scratches seem to disapear. However, if left on the shelf for too long it tends to leave the patches you describe. Always use fresh #10.

The product to remove stubborn dry patches is McGuires #11 (white bottle). It contains an extremely fine abrasive which is excellent for polishing out fine scratches and stubborn #10 stains. The usual sequence is to first use #11 then #10.