The band of invisible light to the right of the visible band is called the infrared, or IR, because those wavelengths are below red (infra-means “below”) in the energy they carry. The band of invisible light to the left of the visible band is called the ultraviolet, or UV, because its wavelengths are beyond violet (ultra means “beyond”) in the energy they carry.
When we see an object, we assume that it “has” a color. For instance, we think that a tomato is red or that a leaf is green or that hair is brown. This is not true. Color is not a property of an object, but a human sensation. The colour we see is the result of five factors:
- The type of light that falls on the object (what mixture of wavelengths it contains).
- The nature of the object itself (which wavelengths it reflects).
- The background against which the object is seen.
- The eye of the person viewing the object.
- The interpretation made by the brain of the person viewing the object.
Of course, people in general agree that a tomato is red. But that is because very similar tomatoes are usually seen by people with similar eyes ad similar experiences, in essentially white (mixed) light, against fairly neutral backgrounds. But if you look at a tomato in the light of a sodium-vapor lamp (whose light contains a very narrow band of wavelengths with no reds), the tomato will appear almost black. Put the tomato back in sunlight, but in front of a very intense, deep red background, and the tomato will look yellowish orange. And how does a tomato look to a color – blind person? To be sure, these are unusual ways of looking for color and are not of direct importance in the salon. They do point out, however, that the quality of light and background, even in ordinary circumstances, can vary enough to make subtle changes in the color an object seems to be at different places and times.
Our brains are wonderfully adaptable devices. They will accept many different softly colored kinds of light as “white” and shift our whole mental scale of color balance to correct for them. It is very important to understand this fact: there is no single standard for what is white light. Daylight is many kinds of white. It is always a mixture of all the colors in a rainbow, but on dull or cloudy days it is more bluish than it is on bright sunny days. The light from an ordinary 100-watt bulb is another kind of white. It is also a mixture of all the colors, but has far less blue and more red than does daylight. The “white” light from fluorescent tubes is still different. This light does not contain a mixture of all colors. Some colors are missing completely. But the balance of the colors that are present is good enough for the brain to accept the light as “white”. The main point, in any case, is this: Anything that gives off, or reflects, even a reasonably good mixture of colors is usually called “white”.
The importance of this discussion is that the operator must make some allowances for lighting in the selection of hair and makeup colors. What type of lighting is there likely to be in the place where the client works or lives? What correction must be made to compensate for the difference between the salon lighting and lighting where the client wishes to look the best? What will be the dominant color of clothing (background) the client will wear then, compared with the color worn to the salon? You should be able to advise your clients of the colors best suited to their skin tones.
The body tissues absorb (soak up) at least part of the energy carried by all of the wavelengths of light. Much of this radiant energy is then changed back into heat. Remember that earlier we said that radiation was one of the ways heat gets from a warmer object to a cooler object? This ability to radiate is particularly true of the longer wavelengths of the IR and red-to-yellowish visible light. As a matter of fact, the only way our bodies know that IR waves are hitting them is by the feeling of warmth those IR waves produce. In mild doses, the warmth from IR relaxes the muscles and lets more blood flow to the exposed skin. Too strong a light of any kind, but particularly too much IR, can cause burns and can dry out skin and hair.
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