This section is from the book "The Hygienic System: Fasting And Sun Bathing", by Herbert M. Shelton. Also available from Amazon: The Hygienic System Vol III Fasting and Sun Bathing.
One of the first things necessary in taking sun-baths is to acquire a good coat of tan. Women and others who do not desire a dark tan on their faces, necks and arms, may cover these when taking sun-baths. In this way they may control the amount of pigmentation in these regions.
Many people are impatient and desire to tan too rapidly. These are inclined to overdo the sunning process and burn themselves. Do not try to get a year's supply of sunning in one day.
There are those who tan readily and those who tan slowly and with difficulty. There are a few who do not tan at all. The amount of precaution required in commencing sunbathing depends upon the type of skin possessed. Brunettes--that is, people with dark hair, eyes and skin--tan most readily and speedily and are less likely to burn easily.
Blondes and red-heads and other individuals with fair skin (usually, also with blue eyes) often find it difficult to tan, but burn easily. These should not be discouraged; for, with patience and perseverence, they, too, may acquire a nice golden-brown skin. It should not be thought that people who tan slowly derive no benefit from the sun.
It is necessary that blondes and red-heads proceed more cautiously in beginning sunbathing. As no good can ever come of sun-burning yourself, all types should use a little intelligence in sunbathing and proceed with due caution. In general, blondes and red-heads do not tan quickly. These have a tendency to freckle (freckling is spotty pigmentation) rather than to develop a uniform tan. With due caution and persistence, most of these may acquire a beautiful tan. Where the tendency to freckle exists, women may desire to cover the face, neck and arms to prevent these parts from freckling. This will detract-little or none from the value of the sun-bath.
Children do not tan as readily and usually nor as deeply as older people. Neither do they seem to burn as easily as adults.
As pointed out elsewhere, we think the chief value of pigmentation is the protection it affords against burning. We would caution those who have developed a deep tan against excessive sunbathing. The statement that "people with a nicely tanned" skin "are able to stay in the sun all day with no bad effects" is misleading and not based on experience.