Yellowing plastic skylights

[blueman]

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

[Frank]

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.

[Paul Drahn]

Frank is correct in all he 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

[blueman]

Paul Drahn <pdr...@webformixair.com> writes:

> On 11/15/2011 3:23 PM, blueman wrote:
>> 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
> Frank is correct in all he 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?

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'

>
> 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 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 would first do what Frank suggested, using some type of plastic polish.

I will try that...

>
> 20 years is probably the normal life for the skylight.

Yes, I know that but it's not leaking so I would prefer not to replace
it now...

[blueman]

Frank <frankperi...@comcast.net> writes:

> On 11/15/2011 6:23 PM, blueman wrote:
>> 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
>
> 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.

I will try that...

>
> 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.

I guess it could be polycarbonate, but I would suspect it's more likely
to be Acrylic...

[micky]

On Tue, 15 Nov 2011 20:18:16 -0500, blueman <NOS...@nospam.com> wrote:

>
>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

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.

[Steve B]

>>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

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

[larry moe 'n curly]

I'm in Arizona, and polyester and acrylic are some of the very few
plastics that are almost 100% resistant to UV exposure, as a check of
car tail light lens covers and clear soda bottles will demonstrate.
OTOH polycarbonate will fog up in about 10 years, as a check of your
car headlight covers will demonstrate. Clear polycarbonate made for
outdoor use needs to be protected with a coating (that coating may be
what turns yellow on headlights), so after you polish up your
skylights with a headlight restoration kit (3M has one, about $10-15),
clean it off with alcohol and then apply a few layers of something
like Krylon #1305 UV Resistant Clear finish.

[Tony Miklos]

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?

[RonB]

You might try something.

We owned a '99 Camry with the clear lenses over the head lamp and park
lamp bulbs. Over time the plastic lenses yellowed and took on a
clouded appearance. A few months ago I saw an advertisement on TV
about a kit that could be used to clear up clouded headlamp covers.
Supposedly it took seconds.

I went out to the garage and got a can of polishing (not rubbing)
compound off the the shelf. After about 30 minutes of vigorous
rubbing they looked as good as new. You might get a can of
automotive polishing compound and give it a try. It might require
some serious elbow grease, or very careful use of a power polisher.

RonB

[Ron]

Those kits are a rip off. I use Turtle Wax premium rubbing compound
or Meguiars scratch remover on my headlights. Takes 30 seconds for
each lens.

[Stormin Mormon]

Is the yellow from tobacco smoke?

--
Christopher A. Young
Learn more about Jesus
www.lds.org
.