A lot of people think they don't need to know anything about applied films unless they work in a science related field. However films aren't only used to change or protect building materials. We can also apply them to our skin to protect us from the sun. These types of films are called sunscreens and we can measure their effectiveness using SPF, or sun protection factor. If you're not sure how SPF works or what SPF you should be using, this article can give you an overview.

Sunlight contains two light elements, UVA and UVB, that can be harmful to our skin if we are exposed for extended periods. UVA rays are longer waves that penetrate more deeply into the skin, triggering suntans and over time, premature aging. However it is the UVB rays that most sunscreen companies and people doing outdoor activities are concerned with. They penetrate the outer skin layers and cause painful burns in minutes or hours. UVB rays are also to blame for skin cancers, though UVA also plays a role.

Wearing a sunscreen will not completely shield you from the sun's harmful rays. Instead, when companies develop sunscreens, they do so with the aim of increasing the length of time it takes you to burn. The SPF or sun protection factor represents how many times longer you will be able to stay in the sun without burning. So a person who normally burns in ten minutes can put on an SPF 10 sunscreen and stay outside for 100 minutes without burning.

The higher the SPF of your sunscreen, the better protected you will be. Today's sunscreens range from 15 to 100 or more, with 60 being the average that you should aim for. Even with SPF 60, it is still necessary to reapply several times per day because sweat, swimming, toweling off, and putting on and taking off clothes after you get out of the pool or at the beach, as it can all rub away your sunscreen and leave you exposed.

When you're considering whether or not to do your activity outside on the front lawn, remember that sunscreens primarily focus on UVB rays, which means being out in the sun is still damaging your skin. You can see this by the fact that you are still developing a tan. Therefore it is always wise to look for a broad spectrum sunscreen, wear a shirt or hat, and stay in the shade whenever possible.