Opacifiers

An opacifier is a substance added to a material to increase its opacity, reducing transparency by scattering light. Opacifiers are used in a range of industries, including paints and coatings, plastics, cosmetics, and foods, where they improve hiding power, brightness, or cloudiness.

Opacity results from light scattering by dispersed particles or droplets within a medium. Effective opacifiers have a refractive index different from the surrounding matrix and are distributed at specific size scales, often in the nano- to micron range. The concentration, size, and uniformity of the opacifying phase influence the degree of opacity and the visual appearance.

In paints and coatings, titanium dioxide (TiO2) is by far the most common white opacifier, providing high brightness and strong hiding power. In plastics, TiO2 is also widely used, with rutile forms favored for durability; other fillers such as barium sulfate, calcium carbonate, and kaolin may be employed to modify opacity, cost, or processing. In cosmetics, opacification is achieved with TiO2 and with pearlescent pigments (often mica coated with TiO2) to produce opacity together with reflective effects; silica and certain polymers can also contribute to opacity in emulsions and powders.

In the food industry, opacifiers are ingredients that create cloudiness or whiteness in products such as dairy substitutes, beverages, and sauces. These may include hydrocolloids, starch derivatives, or other approved food-grade additives that scatter light or stabilize dispersed phases.

Safety and regulation of opacifiers vary by material and region. Titanium dioxide has ongoing regulatory review in some jurisdictions, and nano-scale forms may face specific assessments.