Light Transmittance Range Testing of Packaging Materials

Light transmittance range testing measures how much ultraviolet and visible light passes through packaging materials such as plastic films, rigid containers, and barrier laminates, using methods defined by ASTM D1003, ISO 13468, GB/T 2410, and JIS K 7361. The results help manufacturers balance product visibility against light protection, verify batch-to-batch consistency, and demonstrate compliance with regulatory and customer specifications. Accredited third-party laboratories typically perform these measurements with UV-Vis spectrophotometers and hazemeters across the 200–780 nm spectral range under traceable calibration.

Technical Overview

Light transmittance range testing quantifies the ability of a packaging material to transmit electromagnetic radiation in the ultraviolet (approximately 200–380 nm) and visible (380–780 nm) regions of the spectrum. The key measurands are total luminous transmittance (Tt), the percentage of normally incident light that passes through the specimen; diffuse transmittance (Td), the portion of transmitted light that is scattered; and haze, defined as the ratio of diffuse to total transmittance. Together, these parameters describe the full optical transmission profile of a material rather than a single-point value.

For packaging, this profile carries direct commercial and regulatory consequences. High-transmittance films are required for display windows, lidding films, and transparent bottles where product visibility drives purchasing decisions. Conversely, light-sensitive contents such as vitamins, edible oils, pharmaceutical actives, and certain pigments require low transmittance or selective UV blocking to prevent photodegradation, discoloration, and loss of efficacy. Transmittance range testing therefore supports material selection, incoming quality control, supplier qualification, and compliance demonstrations for regulated packaging in the food, pharmaceutical, and cosmetic sectors.

Testing Samples

Flexible Plastic Films

This category includes mono-layer and multilayer films of PE, PP, BOPP, PET, PVC, PA, and PLA with typical thicknesses of 20–200 µm. Specimens are cut as flat, wrinkle-free sheets and must be free of creases, prints, or surface contamination in the measurement area. Both transparent films and metallized or coated barrier films can be evaluated to determine whether their transmittance falls within the specified acceptance range.

Rigid Plastic Sheets and Containers

Test pieces are prepared from PET bottles and preforms, PP and PS tubs, PMMA and PC sheets, and thermoformed clamshells. Curved container walls are sectioned to obtain flat specimens of adequate size, and thickness is recorded at the measurement point because transmittance decreases with increasing thickness. Where a container cannot be sectioned, whole-container methods using an integrating sphere accessory may be applied.

Barrier and Light-Blocking Laminates

Aluminum foil laminates, metallized PET, opaque PA/PVC blister films, and paper-foil-plastic composites are tested primarily to verify their light-screening performance. For these materials the transmittance range target is typically below 1% across the visible band, and the test is often run as a pass/fail verification against pharmacopoeial-style light-protection limits.

Paper-Based and Biodegradable Materials

Glassine, waxed paper, and cellulose-based films are measured to characterize opacity and to confirm uniformity of coating. Biodegradable films such as PLA and PBAT blends are tested both in their initial state and after UV weathering exposure, for example per ISO 4892, to quantify the retention of transmittance over simulated service life.

Testing Items

Depending on the specification, a transmittance range test report from an accredited third-party laboratory may include the following items:

• Total luminous transmittance (Tt) over the photopic range 380–780 nm, expressed as a percentage.
• Diffuse transmittance (Td) and haze, per ISO 14782, ASTM D1003, and JIS K 7136.
• Ultraviolet transmittance and UV blocking rate, reported for UVA (315–380 nm) and UVB (280–315 nm) sub-bands.
• Transmittance at specified wavelengths, such as 254 nm, 365 nm, and 550 nm, for products with defined sensitivity windows.
• Full spectral scanning from 200–780 nm to identify the wavelength range within which transmittance remains above or below a defined threshold.
• Transmittance retention after aging, weathering, or sterilization cycles.

Testing Methods

Specimen Preparation and Conditioning

Specimens are conditioned to equilibrium in a standard atmosphere of 23 ± 2 °C and 50 ± 10% relative humidity in accordance with ISO 291 or GB/T 2918 before measurement. A minimum of three specimens per material is recommended, cut to the size required by the instrument aperture, commonly 50 mm × 50 mm for hazemeter measurements. Thickness is measured at the test location, and any protective layers, dust, or fingerprints are removed, as surface contamination can inflate diffuse transmittance readings.

Spectrophotometric and Hazemeter Measurement

Total luminous transmittance is determined with a UV-Vis spectrophotometer fitted with an integrating sphere, following ISO 13468-1 (single-beam), ISO 13468-2 (double-beam), ASTM D1003 Method A or B, GB/T 2410, or JIS K 7361-1. The instrument is zeroed against an empty light path or a calibrated reference standard, and the specimen is placed as close as possible to the sphere port without touching it. Haze is measured on a dedicated hazemeter or by the four-port readings of the ASTM D1003 procedure: incident light T1, total transmitted light T2, scattered light with specimen T3, and instrument scatter T4.

Data Processing and Reporting

Total luminous transmittance is calculated as Tt = (T2 / T1) × 100%, diffuse transmittance as Td = ((T3 − T4) / T1) × 100%, and haze as (Td / Tt) × 100%. Photopic values are obtained by weighting the spectral scan with the CIE standard illuminant D65 and the photopic response of the human eye. The laboratory reports individual and mean results, specimen thickness, conditioning details, the standards applied, and a statement of whether the measured transmittance range conforms to the client-defined acceptance criteria. Typical reference values include 88–92% for clear BOPP and PET films, approximately 92% for PMMA, below 10% for opaque HDPE, and below 0.1% for aluminum foil laminates.

Applications

Transmittance range testing is applied across the packaging value chain wherever light interacts with a packaged product:

• Food and beverage packaging: verifying the clarity of bottles, films, and window cartons and the UV screening of edible oil, dairy, and beer packaging.
• Pharmaceutical packaging: demonstrating the light-protective performance of blister foils, strip packs, and amber containers for photosensitive actives.
• Cosmetics and personal care: balancing shelf appeal with protection against color and fragrance degradation.
• Agricultural films: characterizing light distribution properties of greenhouse and mulch films relevant to crop growth.
• Electronics and optical films: incoming inspection of protective films, display windows, and light-diffusing or light-guiding layers.
• Research and development: comparing resin formulations, masterbatch loadings, coating chemistries, and recycled-content levels on optical performance.

FAQ

What does transmittance range mean in packaging testing?

It refers to the set of transmittance values a material exhibits across a defined wavelength band, most commonly 200–780 nm, or to the wavelength interval within which transmittance stays above or below a specified limit. Reporting a range rather than a single value is essential because many packaging polymers transmit visible light well while blocking ultraviolet light, or vice versa.

What is the difference between transmittance and haze?

Transmittance measures how much light passes through the specimen, while haze measures how much of that transmitted light is scattered by more than 2.5 degrees from the incident direction. A frosted film can show high transmittance with high haze; a clear film shows high transmittance with low haze. Both parameters are needed to fully describe see-through quality.

Which standards govern the test?

The principal methods are ASTM D1003, ISO 13468-1 and ISO 13468-2 for total luminous transmittance, ISO 14782 and JIS K 7136 for haze, GB/T 2410 as the widely used Chinese national method, and JIS K 7361-1 as the Japanese equivalent. These methods are technically aligned, so results are generally comparable when specimen preparation and illumination geometry are matched.

How should samples be submitted?

Submit flat material sheets or sections at least 50 mm × 50 mm, with a minimum of three specimens per material and, ideally, rolls of unprinted film. Record the nominal thickness and any surface treatments. For finished containers, laboratories can often cut suitable flat panels from the sidewall.

How long does testing take?

Routine transmittance and haze measurement at an accredited third-party laboratory holding ISO/IEC 17025 accreditation typically requires three to seven working days after sample conditioning, while full spectral scanning or weathering-retention studies may require additional exposure time defined by the selected aging protocol.