Monstro left a question in a previous comment asking what the difference was between Chemical Sunscreens and Physical Sunscreens.
Without going into the virtues of either form of sunscreens, a simple explanation of the 2 different types of sunscreens in the market is as follows.
Chemical Sunscreens are so called because they contain synthetic chemicals which absorb UV rays thereby absorbing radiation. These chemicals work by absorbing UVA or UVB but usually also contain ingredients to block UVA rays. According to the American Melanoma Foundation:-
Chemical sunscreens contain special ingredients that act as filters and reduce ultraviolet radiation penetration to the skin. These sunscreens often are colorless and maintain a thin visible film on the skin. These sunscreens usually contain UVB absorbing chemicals and more recently contain UVA absorbers as well.Continue Reading