Clarity is a critical aspect of product quality in many industries, and modern consumers combine it with color when evaluating whether to buy a product or trust a brand. As a result, scientifically and objectively quantifying haze is essential to achieving quality goals and maintaining customer satisfaction.
What Haze Is and How It Alters Product Appearance
In its simplest definition, haze is reflected light produced by small surface particles on a solid sample. For example, haze in paints and coatings can impact gloss or cause color perception differences. Suspended particles within a liquid also reflect light or change its reflectance direction, leading to turbidity — a cloudy, milky, or opaque appearance.
It's vital to note that haze differs from gloss but can also impact the appearance of high-gloss finishes. Gloss primarily refers to surface roughness — smoother surfaces specularly reflect more light than textured ones, spurring the human eye to perceive more brightness. Since haze scatters light rather than reflects it, it produces a “softer” feel that can lead to glossier surfaces appearing duller.
There are two general types of haze — transmission and reflection.
Transmission haze occurs in transparent goods, like clear plastic preforms or bottled water. As light passes through the sample, factors like surface texture imperfections and impurities scatter the energy, creating transmission loss. Conversely, reflection haze impacts nontransparent products, like opaque sheet plastics. When light encounters the sample, its specular components spread and reflect.
Primary Causes of Haze
Causes of haze typically differ between solid and liquid products.
Many issues can create visible haze in solid goods, including:
- Properties of the pigments used, such as the number of particles and size
- Additive migration or inaccurate dispersion
- Production processes with temperature fluctuations, such as drying, baking, and curing
- Oxidation and aging
- Surface residues
In liquids, a natural interaction between proteins and polyphenols usually causes measurable turbidity. Other potential causes include poor-quality raw ingredients, such as infected barley used in beer brewing or particulate residues from filtering processes.
