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UVA and UVB

UVA (Ultraviolet A) are long-wave rays that usually do not cause burns, but penetrate the skin more deeply. They are thought to be the main culprit behind the wrinkling and leathering of skin. UVA is NOT blocked by the ozone layer.

UVB (Ultraviolet B) are short-wave rays that cause burns. They strike your skin more forcefully, but don’t penetrate deep. UVB is partially blocked by the ozone layer, and the thinning of this layer has caused more of these damaging rays to reach the surface.

You also may have heard of UVC (you guessed it, Ultraviolet C), which are even shorter (and thus more powerful) rays. They are lethal to plant life and small organisms, but are completely blocked by the ozone layer. In the future, this could be a dangerous issue.

Up to a few years ago, sunscreens only blocked UVB rays, but today most “broad spectrum” lotions block both types of rays.

SPF and UPF

SPF (Sun Protection Factor) on a bottle of sunscreen is the amount of time you can stay in the sun before burning. This is based on your skin type, ranging from 5 minutes for very fair complexions to 20 minutes for dark complexions. If you have very sensitive skin, you will need an SPF sunscreen of at least 12 to safety play in the sun for 1 hour (60 minutes divided by the 5 minutes it takes for you to burn). Since you will probably want to stay out for a few hours, it would be wise to use an SPF of 30 to 45. If you plan to swim a lot, you should reapply your sunscreen throughout the day, as they are not fully waterproof.

UPF (Ultraviolet Protection Factor) is a newer rating for clothing, especially clothing designed for sun protection. It measures how much ultraviolet light penetrates the fabric. A UPF of 50 only allows 1/50 the amount of light through.

For the purposes of this article, we will continue to measure clothing with the more-familiar SPF rating.

SPF and Clothing

Now that you have a good idea of the measurements used for sun protection, how does clothing protect you from the sun? Not all clothes are created equal, but it is easy to determine what has low sun protection and what has high.

Thin, lightweight, white cottons offer the least protection. The thinner the material, the easier the UV rays penetrate your skin. The weave is generally looser, allowing gaps in the fabric. Dyes offer more protection, so the darker the shirt the higher the protection.

Polyester, nylon and other synthetic fibers, due to their chemical composition and tighter weave, offer much higher UV protection, in the neighborhood of SPF 20 and above.

Wet clothing, when worn, will offer less protection. Many people will wear a white t-shirt while swimming, but when the fabric gets wet, the SPF factor is greatly reduced. If you wear a t-shirt while swimming, wear one in a dark color.

Washing a cotton garment will actually increase the SPF factor. That’s because the slight shrinkage due to washing and drying will bring the fibres closer together. Also, specialized UV-blocking detergents are now on the market that will temporarily increase the sun protection of the washed clothing.

To estimate the natural sun protection of the fabric, simply hold it up to the sun. If you can partially see through it, that amount of the sun’s rays is penetrating the fabric and the less protection you have.

SPF scale:

3 – An average wet, white cotton t-shirt
7 – An average dry, white cotton t-shirt
10-15 – A green or similarly dark cotton t-shirt
50 – Dark velvet
1,700 – A long sleeve denim shirt or pants
*All numbers are from the American Academy of Dermatology

SPF and Swimwear

Swimsuits need to be fast-drying, light, durable and flexible. This means most beach wear is made of synthetic fibers such as polyester, nylon and spandex, which all have high natural SPF ratings. Like regular cotton, the darker the dye in the suit, the greater the rating. Minimum SPF protection is around 20, meaning that all general synthetics offer adequate protection. Darker colors like blue, red and purple easy reach 50, 100 and higher.

Similar to cotton, the stretching and dampness of the fabric decreases the SPF, though not by a large amount. As most synthetic material has a high SPF to begin with, the lower ratings still offer enough protection. Some materials, when wet, actually increase their protective properties.

Modern swimsuits now range from performance enhancing swimwear using high-tech materials, to swimsuits treated with special UV-blocking compounds, to reduced SPF swimsuits designed to allow you to tan through the fabric.

Tan Through Swimwear

For those who still love their tans, synthetic microfibres or a special blend of Nylon and Spandex allow the sun’s rays to penetrate the skin, but at a controlled rate. Porous material gives the user an even tan over the entire body, and is the equivalent of between SPF 6 and 10. Though the material is thin, it is not see-through. Of course, this means you will be at greater risk of getting a burn, so moderate exposure to the sun is recommended.

UV-blocking Swimwear

A relatively new field, there are now a variety of companies that specialize in swimwear and clothing designed to block a large percentage of the sun’s UV rays. While most materials give adequate protection, these materials are either specially designed with tightly woven synthetic materials and/or treated with UV-blocking compounds for extra protection. They will usually advertise their UPF rating, with 25 and above considered “very good protection.”

Article courtesy of www.no-tan-lines.com - Your source for tan through swimwear
The next time you go to the beach, don’t worry about tan lines! Just wear a tan through swimsuit for that perfect, even tan.