Measurement of Light Reflection and Transmission in Solid Materials
Obtain documentation of your materials' optical properties - from UV protection and packaging light transmittance to quality control of coatings, films, and optical products.
Reflectance and transmittance describe how much light a material respectively reflects and transmits. These optical properties are crucial for product performance, durability, and compliance with regulatory requirements – whether it involves packaging for medical devices, UV filters in sunglasses, or light transmittance in building materials.
Danish Technological Institute measures the reflection and transmission of light in solid materials across the entire relevant wavelength range: from UV light (190–400 nm) through the visible range (400–800 nm) to the near-infrared range (800–1100 nm). The measurements provide you with accurate data for quality control, product development, and documentation.
How can Danish Technological Institute help you?
Danish Technological Institute offers measurement and characterization of optical properties in a wide range of solid materials:
- Total transmittance and direct/diffuse light: separation of the light's path through the material
- Light transmittance of packaging: glass, plastic, and paper containers for, e.g., medical devices or food products. Plastic packaging for pharmaceutical products can be tested according to USP 671.
- UV transmission and UV filtering: testing of sunglasses, ski goggles, and other UV filters
- Light absorption: measurement over a wide wavelength range (190–1100 nm)
- Yellowing, aging effects, and other color changes over time: quantification of color changes over time
- Whiteness and opacity/blocking ability: documentation of materials' ability to block or reflect light
- Reflector characterization: measurement of reflectance for lighting fixtures and optical components
- Clarity and legibility: assessment of visual properties through, e.g., packaging film
- Nanostructured surfaces: measurement of optical properties on specialized surfaces
- Quality control of films, coatings, and membranes: continuous or batch-based documentation
- Gloss and haze measurements: supplementary characterization of surface properties
Why are optical properties important?
A material's ability to reflect, transmit, or absorb light affects both the product's performance and its compliance with applicable requirements. Optical properties are relevant in a wide range of contexts:
Product protection and shelf life: Packaging for medical devices and pharmaceutical products often requires documentation demonstrating that it protects the contents from UV and visible light, which can degrade active substances or compromise sterility. Similarly, food packaging must protect against light-induced quality degradation.
Quality control and traceability: Manufacturers of films, coatings, and membranes use transmittance and reflectance measurements as part of their quality control to ensure uniformity, compliance with specifications, and traceability over time. Yellowing and altered optical properties can be indicators of material degradation.
Regulatory requirements: For products such as sunglasses, medical devices, and building materials, there may be specific requirements for UV transmission, light transmittance, or reflection properties. Documented measurements provide an objective basis for conformity assessment.
Product development and optimization: Optical properties are often considered early in the development process – for example, when selecting materials for optical components, lighting fixtures, or design products where transparency, clarity, or reflection is functionally critical.
Equipment and method
Measurements are performed using a PerkinElmer UV-VIS spectrophotometer equipped with an integrating sphere (Labsphere®). The integrating sphere collects all reflected or transmitted light – regardless of direction – thereby providing an accurate representation of the material's total optical properties.
The equipment covers the wavelength range of 190–1100 nm, which includes:
- UV light (190–400 nm) - relevant for UV protection, aging, and degradation
- Visible light (400–800 nm) – relevant for color, clarity, legibility, and visual quality
- Near-infrared light (800–1100 nm) – relevant for thermal properties and specialized applications
The spectrophotometer enables the measurement of total transmittance as well as the separation of direct and diffuse light; reflectance can also be determined. This makes it possible to characterize materials ranging from transparent films to opaque surfaces.
Who uses these measurements?
The measurement of light reflection and transmission is relevant to a wide range of manufacturers and developers:
- Packaging manufacturers: documentation of light transmittance and UV protection in glass, plastic, and paper
- Medical device and pharmaceutical industry: documentation of packaging light barrier properties as part of the technical documentation
- Manufacturers of optical products: testing of UV filtering in sunglasses, ski goggles, and protective equipment
- Lighting industry: characterization of reflectors and light distribution elements
- Building material manufacturers: measurement of light transmission and reflection in glass, facades, and surfaces
- Food industry: assessment of packaging's ability to protect against light-induced quality degradation
- Manufacturers of films, coatings, and membranes: quality control and material development
Contact us about the measurement of light reflection and transmission
Do you need documentation of your materials' optical properties? Contact Danish Technological Institute's specialist, Lise Dahl Andersen, for a discussion about which measurements are relevant for your product and application.