Haze Meter: Methods, Types and Application

Haze is defined as the scattering of light as it passes through a material, causing a reduction in clarity and a foggy or milky appearance. It is a critical parameter in assessing the optical properties of transparent and translucent materials. Measuring haze is essential in industries where clarity and transparency are vital to product quality and performance. This article explores the methods, types, and applications of haze meters, the instruments used to measure haze.

Haze meter is an instrument used to measure the haze value, light-transmitting and light scattering characteristics of transparent materials. The lower the haze value, the higher the clarity. There are many factors that cause light scattering such as:

• Suspended particles or contaminants within a sample
• Surface roughness due to crystallization
• Inhomogeneity (density difference, fillers, pigments etc.)
• Weathering or surface abrasion
• Porosity of the material
• Mechanical and chemical degradation
• And many others

Haze meters work by projecting light through a sample and then measuring the amount of light that is scattered in different directions. The primary method involves:

1. Transmission Measurement: Light is transmitted through the sample, and detectors measure the amount of scattered light. The difference between the incident light and the transmitted light gives the haze value.
2. Reflectance Measurement: Used less frequently, this method measures the light reflected off a surface to determine its clarity.

Two common standard methods for measuring hazer are ISO 14782 that determines the haze of transparent plastic materials, and ASTM D1003 that determines the haze and luminous transmittance of transparent plastics.

There are several types of haze meters, each suited for specific applications:

1. Laboratory Haze meters: These are high-precision instruments used in controlled environments to provide accurate measurements. They are commonly used in research and development, quality control, and compliance testing.
2. Portable Haze meters: Designed for field use, these devices are lightweight and easy to transport. They are used in on-site inspections and for quick assessments where immediate results are needed.
3. Inline Haze meters: Integrated into production lines, these haze meters provide continuous monitoring of haze in real-time. They are essential for maintaining quality control during manufacturing processes.

Haze meters are most commonly used in packaging Industry such as plastics and packaging films. It can also be used in other industries such as glass, beverages, pharmaceuticals (liquid), photovoltaic modules and cosmetics.

Generally, the haze meter is used in quality assurance (QA) applications, according to ASTM D1003, CIE C – which is the most significant standard used.

Some key applications include:

1. Automotive Industry: Ensuring the clarity of windscreens, windows, and headlights is vital for safety and aesthetic purposes. Haze meters help manufacturers meet stringent clarity standards.
2. Packaging Industry: In packaging, especially for food and pharmaceuticals, the transparency of materials can affect consumer perception and regulatory compliance. Haze meters ensure packaging materials meet the required clarity standards.
3. Display Technology: For screens and monitors, clarity is essential for image quality. Haze meters are used to measure the haze of display panels to ensure they meet the necessary specifications.
4. Plastics and Polymers: In the production of plastic films and sheets, haze meters are used to assess the material's transparency. This is important for applications such as protective films and lenses.