Well, my chemical engineering degree and 40+ years in the engineering plastics world finally paid off! By the way, isopropanol is really bad for any unprotected amorphous ( transparent) plastic such as polycarbonate, acrylic, clear polystyrene. It will cause these plastics to craze and crack within several seconds. Semi-crystalline resins such as nylons are generally resistant to isopropanol. If in doubt, I keep isopropanol away from any unidentified plastic. Good luck!

 

 

Yea guys please dont do this. First, It doest work. Second, if you get any on the silver trim pieces inside the lens you will ruin in.

Ask me how I know. It was a disaster of a project.

Polishing the outside of the lens is your best ROI.

 

So...is the denatured alcohol pictured in my earlier post the wrong type?? And Bruce are you saying to stay away from the inside ?

 

I'm sayin that any cloudiness that appears on the inside of the lens is likely not from anything on the inside surface of the lens. Its just an optical effect. My guess is you have both oxidation on the exterior surface lens and some sort of heat/UV damage to the plastic itself that gives the cloudy/hazy effect when the headlights are on.

The exterior oxidation can and should be polished off with good effect. That will get you 92% of the results. However unless you are a chemist and a surgeon I wouldn't put anything on the inside of that lens. You are risking a $1k headlight to satisfy your OCD.

The issue is the silver plating on the inside trim of the lens is extremely delicate. Its hard/impossible not to get any alcohol on those parts when pouring it in and swishing it around. If any touches it can effect the coating. Within 1 minute I watched 2-3 tiny spots on the bottom edge of the silver trim come off. I had to spend the next 20 minutes cursing and fishing them out of the lens. I also had what looked like water marks left on a couple areas of the silver trim. Luckily only an eagle eye will notice them but I do, and it pisses me off.

And to salt the wound, it didnt do anything to reduce the hazy effect.

Someday I may try to crack open that lens and replace the silver trim with a donor headlight off eBay. But I think its a 50/50 so I would need to be prepared to just buy new headlights or aftermarket headlights if/when that failed.

 

Sorry, posted on the wrong thread!

 

Billy, did you ever confirm if that Klean Strip can of denatured alcohol fuel is the correct stuff to use?

 

Alcohol is NOT compatible with polycarbonate! This includes all alcohols. The amount of chemical attack on the polycarbonate is a function of the stress that resides in the plastic part. The headlights are injection molded, therefore the residual stress remaining in the part is very large. In contact with the solvent nature of alcohol will relieve these stresses in the form of cracks or crazing as it is referred to. For those of you that may have cleaned flat pieces of sheet polycarbonate (or even acrylic ,i.e, Plexiglas which is a totally different chemical, but reacts the same) with alcohol successfully , the reason is the stresses in the sheet are very low and may be below the threshold of the attack by the chemical. Also some sheet products are coated with a scratch resistant (silicone) coating that protects the plastic.
By the way, alcohol is used in the laboratory to determine molded in stresses in polycarbonate. It is best to stay away from any alcohol coming in contact with polycarbonate and even acrylic.
My opinion and experience
30 years as the GE Lexan tech engineer,(retired)

 

Great info.

We're you in Pittsfield during that time when you were a Lexan engineer? I lived there from 75-91 as my Father worked as the Program Manager of Advanced Weapons Systems for the Ordinance Division.

 

Wow - wish I knew that a year ago ^. Amazing.

I assume this is why its nearly impossible to paint the silver trim bits on the steering wheel as well.

 

To Petza914, Short answer is Yes, Pittsfield for a few years 76 to about 81 then off to west coast tech center. Jack Welch was down the hall. Used to go down to Stockbridge , drink beer with Alice, yes, that Alice and Arlo over in Washington (MA). Autocrossed my 911E in the parking lots and on the lake in winter.Fun times, but southern California is home now since 1982

 

Very cool. We lived around the corner from Jack Welch and across the street from Bob Wright (became NBC President) and Jim Cobb (became president of *** Cable). I used to deliver newspapers to a bunch of GE execs growing up.