Why would a polycarbonate skylight haze to the point it looks like
Background: North Florida (Gainesville). About ten years, my mom
replaced the glazing on the large (about 2.5x5') skylight in her
kitchen with polycarbonate, partly on my recommendation. This was done
by getting the piece of polycarbonate cut and fitted into the existing
skylight frame, which dates from when the house was built in 1956, not
by installing a new skylight. My mom died last year, and my sister is
now living in the house.
Today we noticed that the skylight is severely hazed, to the point
that it looks like frosted glass. Some of this could have happened
gradually, but to the best of our memory it's mostly recent. Here's a
photo looking up through the skylight
That's tree branches to the right and blue sky and clouds to the left.
When it was glass, these were clearly visible, as through a window.
Same when the polycarbonate was new.
The top of the skylight feels rough, and looks rough under slight
It's never been cleaned with anything harsh (just glass cleaner),
unless someone has been sneaking onto the property and cleaning things
without the knowledge of the resident. The tree branch overhead is
live oak; currently no other kind of tree hangs over the house.
We tried a couple of forms of gentle cleaning, and nothing helped. It
even continues to look just as hazed with water on it.
While it's true that there are advantages to diffuse light, in this
case the views are good enough that we'd rather it be clear!
Any ideas why this has happened? Or what we could do to prevent it, if
we replace the polycarbonate?
Yes, the ammonia in your glass cleaner reacted with the polycarbonate.
Now go get the appropriate novus polishing kit, and try to polish it back to
clear, or start over with a new sheet and don't put ammonia on it this time.
If you installed the polycarbonate for safety and security reasons, you
could replace it with a new laminate. The glass suppliers have a glass
over poly that has the same strength as poly alone but it is scratch
and chemical resistant because of the outer glass layer. It's not what
would necessarily be called bullet proof but I believe there is a type
that is hurricane proof. If wanted to be really cool, you can get the
electrically controlled transparency glass. If you can't polish it out,
it wouldn't hurt to talk to your local glass supplier to see what they
have. You may be able to get some of the newer scratch and UV resistant
polycarbonate from a plastics or glass supplier.
On Fri, 26 Nov 2010 19:24:04 -0800, "Jon Danniken"
No ammonia has ever touched it. Phew. Nasty stuff.
hmm ... sounds like a plan ...
On Fri, 26 Nov 2010 19:26:18 -0800, Smitty Two
OK, thanks. I had thought of polycarbonate as totally resistant to
sunlight, but obviously that was simplistic thinking. Basically
resistant but with caveats ...
On Fri, 26 Nov 2010 22:27:46 -0600, The Daring Dufas
Not security in the sense of break-ins ... there are much easier ways
to break in to this house. Safety mainly -- protection from broken
glass, protection from whatever flying/falling object broke the glass,
protecting the house from the elements when it breaks.
In a separate skylight investigation recently, I ran across some that
are approved for south Florida -- IOW as hurricane-proof as can be. I
also saw some that are glass, but use the kind of glass used in car
windshields -- I forget what it's called but when it breaks, it breaks
into innocuous granules instead of sharp shards. The glass is supposed
to be extremely strong, but of course does not match polycarbonate.
Cool indeed. I found some. Seems there are three technologies. One
costs about $90/sqft. Another costs about $125/sqft. With about 12 sq
ft in this skylight, those aren't going to happen -- the shade mounted
under the skylight has worked for over 50 years and still works. The
third is predicted to cost only about $15/sqft, but I gather it isn't
available yet. At that price, the shade might get replaced. And
apparently some of these technologies can block up to 95% of the light
while still admitting 80% or more when "open", which actually sounds
better than the shade. "Smart glass" and "electrochromic windows" seem
to be good search terms.
says "The new Boeing 787 Dreamliner features electrochromic windows
which replace the pull down window shades".
The stuff that breaks into small chunks is "tempered safety glass" like
the side windows on a car. A windshield is "laminated safety glass"
meant to prevent you flying through the windshield during an accident.
In commercial buildings, the doors and windows around entrances are
required to have safety glass of either type installed. I've installed a
lot of glass in commercial and institutional buildings. The laminated is
better for security because it holds together making it more difficult
for someone breaking in. You could install regular laminated
safety glass in either standard or what I've installed before called
Solarex which blocks UV. The standard laminated safety glass is not that
expensive and will hold together if broken. It will also be chemical and
scratch resistant. Talk to your local glass supplier, most of those I've
met would be glad to help you out with a small order.
car headlights do this too, you mave be able to polish it out with
buffing compound and electric drill. if you dont mind the work.
start at a auto parts store and try a small area before puutting too
much effort in it
On 11/27/2010 4:14 PM, email@example.com wrote:
On my girlfreinds headlights (uh on her cars headlights) I first tried
novus plastic polishing compound but it wasn't abrasive enough. Then I
used auto paint rubbing compound, followed by polishing compound.
Worked great but the kit is supposed to have a last coat that helps
protect the plastic from future yellowing. I was tempted to spray come
clear coat on them but didn't.
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