Sunscreen Protection and Combining Filters

Regarding your question about Zinc Oxide and combining sunscreens, you are correct that Zinc Oxide is a broad-spectrum UV filter, meaning it provides protection against both UVA and UVB rays. However, as mentioned in the reply, the level of protection offered by a single filter is not uniform across the entire UV spectrum. Some filters might be very effective in certain wavelength ranges but less effective in others.

Combining different UV filters, such as Zinc Oxide and Titanium Dioxide, is a common practice in sunscreen formulations. This is done to create a more comprehensive and balanced protection profile across the entire UVA and UVB range. By combining filters with different absorption or reflection characteristics, formulators can achieve higher SPF (primarily related to UVB protection) and better UVA protection (measured by PA system or critical wavelength), resulting in a more effective broad-spectrum sunscreen than using a single filter alone.

Potassium Hydroxide in Creams

Potassium Hydroxide is indeed used in soap making through a process called saponification. However, in moisturizing creams and lotions, its primary function is often as a neutralizing agent. Many cosmetic formulations use acidic ingredients, such as carbomers or other polymer-based thickeners and gelling agents, to create the desired texture and stability. Potassium Hydroxide, being a strong base, is used to neutralize these acidic components, causing them to swell and thicken the formula. This neutralization process also helps to adjust the overall pH of the cream to a level that is suitable for the skin and stable for the formulation.

So, while it does adjust pH, its role is often tied to enabling the function of other ingredients like thickeners.