Iron oxides are opaque and exhibit with excellent light stability. They are stable in acidic and alkali environments but yellow and black iron oxides are sensitive to high temperatures. Exposure to temperatures as low as 125 – 150°C can cause the color to visibly shift as the yellow will lose some itswater of hydration. They are very opaque and exhibit excellent light stability. The yellow, however, will shed some of its water of hydration at temperatures as low as 125 – 150°C, causing some shift in color that can be seen. Like the yellow, black iron oxide will also shift color, becoming redder, at temperatures of 125 – 150°C. It is also important to know that iron oxide is magnetic and will coat iron or mild steel containers so care should be taken in selecting the proper vessels for scale up and production.
Yellow Iron Oxide
Iron oxides are naturally occurring minerals known to be safe, gentle and non-toxic on the surface of the skin. One of the oldest tricks in the skincare books involve enhancing skin’s appearance with inorganic pigments, such as iron oxides, which typically come in shades of red, orange, brown and black.
Iron oxides are used in makeup, especially eye shadows, blushers, powders, lipstick and mineral makeup. Iron oxides are resistant to moisture, don’t easily bleed or smear and have “staying power” so only a little application is needed.
Iron oxides won’t irritate the skin and aren’t known to be allergenic, so sensitive skin types you can put your guard down.