[Ingredients in Ivory Soap:
Sodium tallowate (cleansing agent derived from beef tallow), Sodium cocoate or sodium palm kernelate (cleansing agents derived from coconut or palm oil), Water, Sodium chloride (salt), Sodium silicate (soluble glass), Magnesium sulfate (epsom salts), Fragrance
I had a lot of trouble finding that. It seemes like a typical ingredient label for a soap. The first two ingredients are traditional soaps (metal salts of fatty acids).
Ivory pH = 9.5
(water pH = 7)
True, Ivory has an alkaline pH and would thus seem like it would be harsh on the skin. However, the pH of something doesn't neccessarily speak to its total or net alkalinity. In fact, there is apparently little actual "free or available alkalinity" in Ivory soap.
"Available or free alkalinity is simply the concentration of alkalinity that is not tied up in formulation and is free and available to do work. Available alkalinity concentrations are measured by percentage. Common household detergent systems have no available alkalinity compared to instrument detergents. For example: Ivory Soap has a pH of 10 which is high on the alkaline scale but has no free or available alkalinity and, therefore, is safe enough to wash your face.
Theoretically Ivory soap should have a relatively low free alkalinity. But what happens when the soap dissolves in water??
The free alkalinity is usually determined using the ethanol method or the barium chloride method. In ethanol method soap is dissolved in neutralized ethanol, and the free alkali is titrated with an ethanol solution of HCL. The barium chloride method includes forming a precipitate of soap/carbonate by using barium chloride and determining resulting the alkalinity of the solution, which represents the alkalinity of the redsidual free metal hydroxide.
However, while it is true that many soaps have a low level of free alkalinity (compared to something like dishwashing detergant that utalizes a high level of free alkalinity), the pH (amount of free hydrogen ions in solution) is an indicator of how basic or acidic something is. Remember soap is water soluble to a certain degree. Alkaline water soluble substances cause the concentration of hydroxyl ions (OH-) in water solutions to be higher than the concentration of hydrogen ions (H+). Soap has a pH of say 10. So when soap dissolves in water there are more (OH-) ions in the medium than (H+) ions.....so it doesn't matter if the total free alkalinity in the soap is low, the pH is still high, and can cause fatty acids in the skin to loose (H+) ions.....
Ivory soap wouldn't have been my product of choice in order to conclusively demonstrate your point that 'excessive washing' or cleansing of the skin doesn't make a difference in sebum production levels. In any case, I think the test would have been more convincing if you had used something a little more harsh...
Maybe he should have used some dishwasher detergant...or maybe straight sodium lauryl sulfate...that's strong stuff.....
And then there's also the larger more significant issue (that possibly you weren't concerned with during this experiment) of the interplay of sebum production and acne. I'm playing devil's advocate here, but maybe the skin's regular sebum barrier is more effective at staving off acne when it is undisturbed rather than having it constantly replenished after cleansing/stripping (because of increased chance for bacteria to penetrate surface without the barrier.)
Sorry my friend, there is no such thing as skin's sebum barrier. Little kids hardly have any sebum. Oh and the palms of your hands and the soles of your feet have no sebceous glands either. Sebum does not form a protective barrier on the skin. The skin's barrier is actually maintained by layers of overlapping corneocytes, with alternating lipid bilayers and water layers in between. The barrier is reinforced by other epidermal lipids, like ceramides, and humectants that draw water into the skin. Epidermal lipids are not sebum. They are something entirely different.....however washing the skin removes both types of lipids, which can damage the skin's barrier function.....