Yellowing plastic skylights

We have a couple of non-standard sized skylights that are yellowing with age. They are probably 20+ years old. I'm not sure if they are acrylic or some other plastic.
However, they have turned yellow/amber with age presumbably due to the effect of sunlight exposure.
Short of replacing the domes with new custom-sized ones, is there any way to remove the yellowing by treating the surface (either chemically or mechanically) or is the yellowing intrinsic to the plastic?
Thanks
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 11/15/2011 6:23 PM, blueman wrote:

Acrylic does not yellow. Sun is not kind to plastics and there may be other degradation warranting replacement. You might try buffing with a mild, fine abrasive. There is stuff for headlights at auto stores but I suspect color is throughout.
Q. Does acrylic (Plexiglas, Lucite) yellow in the sun?
Since the beginning of the creation of plastics, many myths have been perpetuated about the longevity of plastics, especially outside in the elements. All plastics come from petroleum and natural gas. Sunlight, especially ultraviolet radiation, has a disastrous effect on most plastics. Some plastics, like polyethylene (PE) milk jugs, degrade quickly in the sun - in a matter of months. PE can easily be recycled. Many children's toys are made from PE and get brittle and crack when left outside.
Acrylic (Plexiglas, Lucite,and Acrylite) comes from natural gas and is completely inert when in solid form. American-made acrylic does NOT yellow in the sunlight. Witness the protective canopies and bubbles in the World War II bombers - they are still clear after 50 years in the sun! There are three other clear plastics that do yellow in the sun and get confused with acrylic - Styrene, PETG, and Polycarbonate. They have their respective qualities that make this an acceptable trade-off. Ask your Ridout Plastics salesperson for information on all of these plastic solutions.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I will try that...

I guess it could be polycarbonate, but I would suspect it's more likely to be Acrylic...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 11/15/2011 3:23 PM, blueman wrote:

Have you examined the skylight closely from the roof side? Do they have two sheets of plastic making a sandwich with air/gas between the two? Keeps condensation down. If two, is only the outer sheet yellowing?
Do you live in a heavily forested area where tree pollen may have slowly accumulated on the outer surface? How often do you wash the skylight?
I would first do what Frank suggested, using some type of plastic polish.
20 years is probably the normal life for the skylight.
Paul
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

There are two layers with an air gap and the outer layer seems to be the most yellowed. Actually, it's a combination of 'yellowed' and 'dull'

I live in suburbia though there are some maple trees around. I rarely clean them since the roof is 35 feet up. But I did clean it today with 409 and while it removed a lot of 'black', the resulting clean surface was still yellow and dulled.

I will try that...

it now...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

409 and Fantatic are probably really good for grrease, and even better for the crinkle surfaces on TVs for many years (when sprayed on, but not when wiped on), but I don't think it's nearly as good as a lot of other clearners. Different kinds of dirt require different clearners.
and while it removed a lot of 'black', the resulting clean surface

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Maybe try some of that car headlight plastic restorer they sell on TV. I mean, if it's on TV, it HAS to work.
Right?
I'd say, though, that it's time to start thinking of replacement. 20 years of solar strength UV will kill the best of plastics. Careful with that cleaning. Typically, all is fine until we get up there and start messing with stuff ........
Steve
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 11/15/2011 6:23 PM, blueman wrote:

I've heard numerous reports about the headlight restorer kits not working very well so on something as big as a skylights you would probably need 20 kits and still have crappy results.
I've had excellent results restoring yellowing headlights by wet sanding them with 1000 grit paper, then with 2000 grit, then polishing them. I showed them to someone who tried the kits and he said mine look 100 times better, almost as good as new. It may work on your skylights?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.