Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: Jaclyn9189 on 19/02/2013 19:28:00
-
I recently had a film added to my car windows that is supposed to
block 99% of UVA/B rays. Before adding the hilm, I had an old receipt on my dashboard that was folded in half. On the half that was exposed to the sun, the ink was faded and yellow (when it used to be black). On the side that wasn't exposed (it was facing down), the ink was pretty much intact. I figured it was the UV radiation breaking the bonds in the ink molecules, so I decided to do a test to see if my UV-filtering window film worked by flipping the receipt over and exposing the intact side. 2 months later and I'm noticing that the ink is starting to fade like the other side had. Is the film not doing what it claims to do or could there be some other culprit in the sunlight fading the receipt?
Thanks!
-
Question: How long was the receipt exposed to the sun on the original side?
The film only claims to block 99% of UV light, so the receipt should last about 100x longer, if this were the only effect.
However, ordinary glass absorbs and reflects a fair amount of UV, so the film won't make a difference of 100x to the total UV exposure.
If you sometimes drive with the window open, a lot of UV will get into the car around the UV film.
-
Also, heat will cause some distortion of the ink's color. Not to mention general aging, such as how old newspapers often turn yellow, though this could take into account a multitude of factors. Furthermore, humidity in your car could cause ink chromatographization on the receipt.
-
Some receipts may be printed on thermal paper, and tends to be extremely sensitive to light and heat which may not be the case with other types of ink.
It may not be UV that is damaging your paper, although UV is more damaging to a number of things.