The cosmetics industry racked up sales of about $170 billion last year. That may seem like a lot of liquid eye liner, but the segment still shows strong rates of growth. Underlying every successful cosmetic product is the ability to deliver consistent quality every time it's purchased by a consumer. Understanding how moisture affects quality can help you achieve the quality your customers demand. If you need a refresher on how moisture and water activity are related, click here.
Many cosmetics products are compacted tinted powders. The compaction and flow properties of these substances are controlled by water activity. During the manufacturing process, knowing the critical water activity of your powder can assure that your equipment isn't loaded full of a powder that won't move. When the blended powder is ready to be formed into the packaging, the water activity influences how tightly the powder is compacted. Any variation in your product's water activity will affect its physical properties.
Water activity, and not mositure content, determines what bacteria can grow in your product. Cosmetics tainted with bacteria can cause irritations and infections on the skin and in eyes. Even if your products comply with GMP requirements, your customers may not be as careful. Formulating your product with a water activity below 0.87 aw will guarantee that even if it picks up trace amounts of bacteria during use, the bacteria won't grow.
Many cosmetics maufacturers monitor the moisture content of their products. Why? That's what they've always done. For a particular product, water activity and moisture are linked: if one goes up, so does the other. So even if you just want a better way to measure moisture, water activity can give it to you. Why?