WHAT ARE ULTRAVIOLET BRIGHTENERS

They are called Blueing, Brightening dye, Optical Brightener, FWA (Fluorescent Whitening Agents), Color Safe Bleach, and Laundry Enhancers. They are actually a UV Dye used to collect energy from a wide range of Ultraviolet and short blue wavelengths and reradiate that energy in a powerful peak at about 440 nanometers. (See graph on inside front cover.) Notice that 440 nm. light is almost invisible to humans while near maximum sensitivity of the deer.

There are about 200 compounds used and most are permanent. Fabrics like the poly/cotton blends, commonly used in camo, are almost always pre-brightened when manufactured. This is because the printing and colors will be brighter and more attractive if applied to bright fabric. Because it is easier and cheaper to brighten clothes than to clean them, all detergents (except Sport-Wash) contain Ultraviolet brighteners. Many water repellents especially factory-applied polymer types are applied with extenders that function as brighteners.

Deer are much more sensitive than humans to the shorter wavelengths of light. They have a blue cone with peak sensitivity at 455-nm, just 15 nm from the 440-nm peak of spectral power caused by the UV brighteners. This is earth shaking news to a 2 legged predator that can’t imagine the brightness of light he barely sees. This 440-nm light is seen as bright blue by the dichromatic eye of the deer. It occurs on garments of any color from camo to blaze orange if UV brighteners are present. In very low light the deer, like a human, switches to rod (black, white, and gray) vision and the 440 nm light caused by the UV brighteners is seen by the deer as a bright white.

Game animals quickly learn to respond to the glow of brighteners just as they would to the smell or sound of the hunter. If it glows, it’s a human; and the bigger the buck, the less chance you have of seeing him if you glow.

I have often observed that northern guides were very successful in stalking game animals. The one thing they all had in common was the wearing of woolen garments in plaids, browns and greens. They blended into the background because natural wool does not contain UV brighteners and therefore does not respond to UV light. Wash your Wool garments in Sport-Wash or have them dry cleaned. (Woolite® now contains UV brighteners and must be avoided like all commercial detergents, softeners, and color safe bleach.)

You can observe, for yourself, the effect of UV brighteners on your own camo, if you have access to a fluorescent UV light. Simply hold your camo under the light and see if it glows. If it does, spray it with U-V-KILLER and watch the UV brightness disappear. This is not magic, it’s technically simple, you are covering the brightening dye with a blocking dye, and if you have a UV light, you can watch it happen. You can buy a 350 BLB Fluorescent Light from Atsko or most home center stores. You can practice viewing different samples of white paper and cloth. Placing a drop of U-V-KILLER on a swatch that glows will immediately darken it. Now observe this spot under ordinary light and you begin to understand how little we see of the brightener effect. Deer by contrast, are perfectly designed to see the effect of UV brighteners without the aid of an artificial light source.

Fabrics like the poly/cotton blends, commonly used in camo, are almost always pre-brightened when manufactured.