Plexiglas "fogged up"

[clif]

My Case 880B excavator seems to have Plexigas or some thing like that for windows, but you can not see out of it.  It is like they are "fogged up" but you cannot wipe it off is there a way to make them clear again or do I have to replace them, if so with what?  Thanks!! Clif

[Jeff]

Anytime they got like that in our equipment like the debarker booth window and my slide sawbooth window, we had to replace them. Unless someone knows of a miracle polish.

[clif]

I kind of figured that was going to be the answer!  Sigh!!!  (-;

[Brian_Rhoad]

There is a cleaner/polish made for convertable top windows that may work. Head light reconditioner. Plastic polish. Tooth paste with baking soda might work also. Or baking soda mixed with water or vinegar.

[Larry]

You might give this a try.

http://www.harborfreight.com/12-minute-headlamp-lens-restorer-kit-65938.html

If you use it give us a report on your success...or failure.

[Stan snider]

Use  clear liquid floor wax. It will surprise you.  Stan

[John Mc]

Small aircraft use plexiglass windows. There is a polish sold to take out scratches and such. It may work OK on haze as well. If you do a search on "Aircraft Spruce & Specialty"  or on "Sporty's Pilot Shop" you should find something.

A few tips for avoiding the problem (garnered from years of cleaning my Cessna 172's windows, and reading up on how to do it right to avoid the problem):

• Do NOT use Windex or other window cleaners on plexiglass. The ammonia in them attacks the plexiglass, eventually causing the haziness or fogging you mention.
• Do not use paper towels clean the plexi. The small wood chips/fibers in the paper towels are abrasive to plexiglass. This is true even of the "soft" paper towels (i.e. "Bounty"), not just the cheap ones you find in the restaurant bathrooms. You probably won't notice it the first time you do it, but the effect is cumulative
• Try clean cotton cloths, or even better the cleaning "shammy" cloths sold by auto stores for cleaning high-end autos -- some of those owners are completely nuts about babying their pride and joy. Resist the urge to reuse that same cloth you used last time that has been sitting in your shop. It only looks clean enough.
• Soak the plexi in plenty of water before cleaning to soften the bugs and whatever else is clinging to it
• a quick spray and wipe with lemon pledge when you are done cleaning the plexiglass will make it easier to remove the bugs and other crud without having to scrub so hard (and scratch) your windows. This or other waxes may also temporarily make plexiglass look better, but the scratches are still there, and it wears off quickly.
• Some plexiglass is more sensitive to UV light than others. UV exposure can cause fogging or crazing. If you are replacing the windows, it might pay to look into what kind of UV resistance the stuff you are buying has.

For more tips, stop by a local small airport and talk to the aircraft mechanic or some of the owners. Replacing aircraft windows is ridiculously expensive (makes those Stihl parts look downright reasonable). Anyone who has been around small aircraft for a while will have picked up some good techniques.

If you want to see an aircraft owner have a heart attack, watch his reaction when the helpful lineboy at some airports walks over to clean the owner's windows with a bottle of Windex in one hand, and a roll of paper towels in the other.

John Mc

[IMERC]

chances are you have polycarbonate rather than Plexiglas...

Windex and/or some similar item fogged them.. the UV exposure didn't help much either...
auto parts stores sell lens cleaner/polish for headlight lenses... maybe one of those kits will work...

[Chuck White]

John Mc is spot on!

On my first hitch in the Air Force, I was an Aircraft Mechanic.

At that time, the aircraft canopies were made of plexiglass and they would get what's called "crazed" (tiny checks or cracks) and we had what was labled "plexiglass cleaner"to take care of it, it also remove static electricity too!

You might just do a Google search on "plexiglass cleaner"!

[Jeff]

It probably costs more then a square chunk of replacement plexiglass. ;)

[clif]

Thanks for the thoughts and tips, at this point I was thinking it would not hurt to try the belt sander!! :D :D  Clif

[John Mc]

It probably costs more then a square chunk of replacement plexiglass. ;)

That scratch polisher the aviation sites sell isn't cheap... but then again, neither are replacement aviation windshields. Even the flat windows are expensive, but the front windshield has multiple compound curves. I guess they've got to have something for when some sue-happy moron takes them to court after colliding with someone/something since he couldn't see clearly through the layers of bugs and crud on his windshield that he was too lazy to clean off.

[Gary_C]

Most likely the material you have in those windows is a polycarbonate which is generally known as Lexan. Polycarbonates are very tough and can be moulded or bent into shapes. It is the most commonly used plastic in those impact resistant windows.

Plexiglass on the other hand is sheet stock only and is more brittle and cannot be easily formed or bent. Just try to drill a hole in a plexiglass sheet with an ordinary twist drill and you will see how easily plexiglass can crack.

As far as the clouding or crazing in lexan, I am trying to deal with both problems right now. My front harvester window has crazing on the outside which I believe is from sitting in the sun too much and from being bent into a slightly curved shape.  I bought a plastic cleaner and it has helped but I just found out the dealer has been fixing some of these windows with a plastic cleaner and a big buffer. So far I have just done the polishing by hand and with limited sucess.

On the clouding issue, the headlight lenses on the wife's car has this problem. Some people claim it is caused by mineral deposits from water and recommended the use of either an acid cleaner or that Iron Out product. So far, I have just used the plastic cleaner and it has helped somewhat but has since come back again.

Next thing I am going to try is one of those auto buffer/polishers. If it works on those two vehicles, next I have to work on the cloudy windows in my Hydroaxe.

That plastic cleaner is still far cheaper than  replacing those windows.

[gary]

I have used transmission fluid to clean fogged headlights with good results. I don't know why it works but it does seem to make difference.

[Stan snider]

Gary; that may be because the oil in it fills up the million microcracks that are on the surface,thereby changing the refractive properties. Somewhat simular to being able to see through a glass of water better than the same glass empty. That is why the liquid floor wax works, because it fills in the microcracks. Hope this makes sense. It will work on an old pair of sunglasses or goggles too. Stan

[John Mc]

Plastic cleaner generally will not correct the problem, just cover it up temporarily. However, cleaning the plexi/lexan properly will help prevent it from happening. Wood dust and grit will cause problems if you just try to wipe it off (especially if you try to wipe it off dry) - it's the same effect as trying to clean with a paper towel. You might not notice it after one or two cleanings, but eventually all those tiny scratches add up.

A polish (not a cleaner) is the only way to get rid of them. A good system will work you down through ever finer grit in the polishes until you have a like-new surface.

Protect it from UV, and keep it clean using proper techniques, and it will last a lot longer. Aircraft stored outside often have covers installed over the cabin to protect the windows (as well as the interior) from UV. In windy areas, sometimes the covers themselves or the dirt attached to them will scratch the window as it flaps in the breeze. There has been a lot of effort put in to holding the covers tight ans still, as well as figuring out what to line the insides with where they contact the window to minimize abrasion.

Lexan/plycarbonate is usually formed hot, so it should take that shape without crazing (unless your manufacturer tried to cold-form it, Gary??).

John Mc

[Gary_C]

Lexan/plycarbonate is usually formed hot, so it should take that shape without crazing (unless your manufacturer tried to cold-form it, Gary??).

John Mc

That's one of the advantages of Lexan that it can be formed at relatively low temperatures. But when you do form it into an outward curved winshield, there are stresses on the outer surface because of the stretching of the outer surface. Then after about eight years of being out in the sun, those minute cracks can appear. The easy way is to just replace it, but it ain't the cheapest way.

So I am going to give it one more try with a buffer before I go the expensive way. Or avoid working toward the sun as that is the only time you can really see those cracks.

[LeeB]

I would think a good high quality automotive clear coat polish and a buffer would do the trick. You can also take it out with heat but it's a real thin line between enough and too much. Basically you melt the outer surface enough for it loose the crazing. Tough to do with out burning.

[roger 4400]

Hi ! what I know is that plexiglass will get a yellowish tint with years and can scratch easy. What I use is called LEXAN and it does not get yellow and is resistant. They use it in prison or on aircraft. ......but nothing is perfect it is more expensive than plexiglass. have a nice day. Roger

[clif]

Ok! Ok! So I will trade the belt sander for a polisher and give it a try this weekend.  Thanks again for all the imput.    Clif

[John Mc]

... But when you do form it into an outward curved windshield, there are stresses on the outer surface because of the stretching of the outer surface. Then after about eight years of being out in the sun, those minute cracks can appear. The easy way is to just replace it, but it ain't the cheapest way.

I've seen that on some aircraft windows, but usually they are a whole lot older than 8 years before they show that problem (and these windows have some rather tight-radius bends in some places). Some of those cracks go pretty deep, and can't be polished out.

[StephenRice]

Clif,

If you get this before you fix your windows, try this.  It is a tip that I learned from a detailer friend of mine at a used car lot that they use to rejuvenate headlight covers to like new condition.  I tied it on mine and it worked great.  In fact, other people have had me fix their headlights now.

Instead of getting some expensive repair kit or special polish, get some sort of buffer.  I personally bought a 6" buffer that you put into a drill and it cost me a whopping $3 or $5.  Then, use chrome polish.  Regular buffing or polishing compound will likely be too abrasive.  I bought my chrome polish at Walmart for around $3.

Then, use the buffer with liberal amounts of chrome polish to remove all of the scratches and oxidation from the Lexan or Plexiglass windows that you have.  One IMPORTANT word of caution, however...  Be careful not to spin the drill too fast and too long in one spot or you may build up too much heat and actually begin to melt the plastic!  I did that once.  If you do accidentally begin to melt the plastic in a spot from spinning the buffing pad too fast, then simply get some fine sandpaper or emery cloth and sand the melted buildup off along with the big scratches, then return with the chrome polish to remove the scratches made by the sandpaper.

All in all, with a little elbow grease and patience along with an electric drill with a buffer attachment (or a regular buffer) along with $3 worth of chrome polish and you ought to be back in business with pretty clear windows once again.

For what it is worth, I hope this helps you...

[clif]

Thanks Stephen!  It has been raining all morning and may not stop until Monday so I have not tried any thing yet, but Your suggestion sounds worth a try and I will be heading to town in a little bit and pick up some crome polish and then hope for a break in the weather !

[StephenRice]

Try to do just a corner of one window where it is not that important before you tackle the whole project at once.  That way, you can see if it is going to work for you.  Also, if you are using a drill or angle grinder mounted buffer versus a regular buffer, then I might suggest you try to adjust the speed down just a bit to try to prevent burning the plastic.

Hope it works for you!  I did the headlight covers on my pickup in the picture on the side and it worked great.  DO be ready to either pressure wash or not worry about the nearly unavoidable polish flecks that will get flung all over your backhoe.  ...  Just a heads up...

[DouginUtah]

This morning there was a cable channel show called "Trucks". I just caught the tale end of it. They were restoring a headlight using toothpaste and a buffer. It came out looking really good.