To understand the tanning process of the skin, it is essential that you—the salon owner or operator—understand light and how it works. The influence of light on the development and life-sustaining effects for mankind is not a simple concept. People and animals always have been subjected to various physiological responses due to the effects of sunlight. With the passage of time, researchers are finding that light, whether it be natural or its artificial equivalent, plays a part in many significant physiological and biochemical reactions.
To understand the full consequences of light, it is necessary to have an understanding of the electromagnetic spectrum—a spectrum of a continuous range of radiation spreading from cosmic rays, up through the ultraviolet, visible and infrared regions to radio waves.
Measuring Light
Light is a wave-form energy source measured according to the size of its wavelength. A wavelength is the distance between the crests of two consecutive electromagnetic waves and is measured in nanometers. A nanometer is equal to 0.000001 millimeter, which is onemillionth of a millimeter. The solar radiation reaching the earth is made up of rays of varying wavelengths.
Visible Light
One portion of the spectrum is visible light, which first was discovered in 1665 by Sir Isaac Newton. At that time, it was thought to be one band of light, but later it was found that it was a combination of many colors. And now, in a rainbow or when a beam of light strikes a prism, it’s apparent that it truly is a combination of many different colors. The multicolored rays spring forth as red, orange, yellow, green, blue and violet. These are known as visible radiation. Visible radiation is that portion of the spectrum between 400 nm and 750 nm.
Ultraviolet Light
Ultraviolet light is not visible to the human eye. It is defined as that part of the spectrum below 400 nm. The ultraviolet spectrum can be further divided into four bands: UVA, UVB, UVC and UV Vacuum. UVA rays are the longest ultraviolet rays, while UV Vacuum are the shortest. Since different ultraviolet wavelengths produce markedly different physiological and therapeutic effects, these groupings are based on general biological and physical effects of radiation from each region.
UVA Light
The UVA range abuts visible light and often is referred to as near-UV or “black light.” UVA1 covers the region of 320 nm to 340 nm; UVA2 covers the range of 340 nm to 400 nm in wavelength. UVA light acts primarily to darken melanin pigment granules already present in the skin tissue. In the amount permitted in indoor tanning, it causes little or no perceptible erythema. Because UVA tans with little or no danger of sunburning, the development of equipment utilizing primarily or exclusively UVA emissions revolutionized the indoor tanning industry. This light accounts for the majority of the UV output of low-pressure equipment and virtually all of the output in high-pressure units.
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