Clouds can be miles across, and weigh billions of pounds, but they are only made of a little dust and water! Water has the interesting property that it is clear to our eyes. It absorbs only a little light in the visible spectrum, but much more in the infrared. If our eyes worked in the infrared, water would appear more as a door than a window, as it would block out some of the light becoming opaque.
Below is a graph of the absorption of water along a portion of the electromagnetic spectrum.
There are three different types of UV light which are classified according to their wavelength: UVA, UVB & UVC:
• UVC (100-280nm) is the most damaging to our bodies, but it is mostly filtered out in the atmosphere by water and ozone – if it were to reach us, it would certainly be fatal.
• UVB (280-315nm) is the type of radiation responsible for delayed burns on our skin, and contributes to skin ageing, and growth of cancer cells. Again, we are protected from most of this light by a healthy ozone layer.
• UVA however, is very weakly absorbed by the atmosphere, and at 315-400nm, it is right at the dip on the graph above. This means it can penetrate directly through cloud cover and burn our skin, any day of the year. This type of radiation can cause a range of effects; from mutations to sun bleaching. Year round these rays penetrate the earth with over 90% of UVA light reaching the planet. This is not a bad thing however, as plants use the UV to photosynthesize and make food and oxygen for the rest of us mammals – and radiation from the sun, and other suns, is what makes random mutations in our genetic code giving rise to the multitudes of life on planet Earth.
For things that are not constantly regenerating such as photographs, shower curtains, and even labels, this barrage of radiation will damage, fade, and weaken the materials. Just like sunscreen on a sunny day at the beach, a label that is outside all year will need some protection. Here at Electronic Imaging Materials, Inc. we have “SPF” product – #457, a UV resistant laminate that can cover and protect any label, as well as a wide range of labels that can take the use and abuse of outdoor exposure – rain or shine.