Packaging Aging Color Change Determination: Test Methods, Standards, and Applications

Color change is one of the most visible and commercially critical indicators of packaging degradation, affecting brand identity, shelf appeal, and regulatory compliance. Determination of color change after aging uses controlled laboratory light, heat, and humidity exposure combined with instrumental colorimetry to quantify fading, yellowing, and discoloration. This article explains the sample types, test parameters, standard methods, and evaluation criteria used by accredited third-party laboratories for packaging aging color change determination.

Technical Overview

Packaging materials are continuously exposed to ultraviolet radiation, visible light, oxygen, heat, and moisture during production, storage, transport, and retail display. These environmental stresses drive photolysis, photo-oxidation, and thermal oxidation of polymer substrates, pigments, dyes, printing inks, and surface coatings. The macroscopic result is discoloration: fading of printed artwork, yellowing of white and transparent plastics, bleaching of metallized layers, or browning of paperboard.

Color change determination quantifies these effects objectively. Specimens are measured colorimetrically before and after accelerated aging, and the difference is expressed in the CIELAB color space as ΔL* (lightness), Δa* (red-green axis), Δb* (yellow-blue axis), and total color difference ΔE*ab. Supplemental metrics include CIEDE2000 (ΔE00) color difference, yellowness index, whiteness index, grey scale rating, and gloss change. By correlating accelerated exposure with real-world conditions, manufacturers can validate UV stabilizer packages, pigment systems, ink formulations, and protective coatings, and can establish shelf-life and display-life claims.

The most widely applied framework combines exposure standards such as ISO 4892 (parts 1 to 3) and ASTM G151, G154, and G155 with color measurement standards such as ISO 11664, ASTM D2244, ASTM E313, and, for Chinese market requirements, the corresponding GB/T 16422 and GB/T 11186 series.

Testing Samples

Plastic Films and Flexible Laminates

Monolayer and multilayer films made of PE, PP, PET, PA, PVC, and EVOH, as well as foil-containing laminates used for food, beverage, and pharmaceutical flexible packaging. Free-standing film coupons are typically cut to at least 50 mm × 100 mm, mounted on inert holders, and exposed without tensile load. Laminated structures are tested in their as-produced configuration so that interlayer interactions, such as migration of UV absorbers from adhesives, are captured.

Rigid Plastic Containers and Preforms

Bottles, jars, closures, tubs, trays, and injection stretch blow-molded preforms made from PET, HDPE, PP, PS, or PC. Whole containers may be exposed directly with careful rotation protocols to ensure uniform irradiation, or panels may be sectioned from container walls. White, translucent, and tinted containers are prioritized because they exhibit the most noticeable yellowing and shade drift.

Printed Labels, Sleeves, and Folding Cartons

Pressure-sensitive labels, shrink sleeves, in-mold labels, and printed paperboard cartons with flexographic, gravure, offset, or digital inks. Colorfastness of printed color patches, brand-critical spot colors, and bar-code contrast areas is assessed. Specimens are prepared in duplicate so that exposed and unexposed reference panels can be compared side by side.

Paper, Paperboard, and Metal Packaging Coatings

Uncoated and coated paperboard, barrier-coated papers, varnished metal can stock, and aluminum substrates with lacquer or printed coatings. These samples are evaluated for yellowing, brightness loss, chalking, and coating discoloration following the same exposure and measurement sequence used for plastics where applicable.

Testing Items

The core measurable outputs of a packaging aging color change determination program include:

• Total color difference ΔE*ab and ΔE00 (CIEDE2000) between unexposed and aged specimens
• Directional color coordinates: ΔL* (lightness/darkness), Δa* (red/green shift), Δb* (yellow/blue shift)
• Yellowness index (YI E313) for white and near-white substrates and coatings
• Whiteness index for brightened papers, films, and containers
• Grey scale rating for change in color, typically rated 1 to 5 in half steps per ISO 105-A02
• Gloss retention at 60° and 20° geometries, which frequently accompanies color change on coated and printed surfaces
• Visual assessment of fading, blooming, chalking, delamination, and metamerism under standardized D65 illumination

Testing Methods

Specimen Preparation and Baseline Measurement

Samples are conditioned to equilibrium in a standard atmosphere of 23 °C and 50% relative humidity in accordance with ISO 291 or the equivalent conditioning clause of the applicable GB/T standard. At least three replicate specimens per material and condition are prepared. Baseline color values are recorded with a calibrated spectrophotometer using a D65 illuminant, 10° standard observer, and either d/8° sphere geometry (SCI or SCE mode, consistently applied) or 45°/0° geometry. Opaque samples are backed with a standardized white or black backing; transparent films are measured over defined white and black backings to separate transmission and reflectance effects. Measurements are taken at multiple marked positions to enable re-measurement at identical points after exposure.

Xenon Arc Lamp Exposure

Xenon arc weathering per ISO 4892-2, ASTM G155, ASTM D2565, and GB/T 16422.2 provides the closest spectral match to full-spectrum sunlight and is preferred for retail-display simulation and outdoor storage scenarios. Test conditions typically use daylight filters with an irradiance of 0.51 W/m² at 340 nm, a black panel temperature of 63 °C to 65 °C, and a cycle of 102 minutes light followed by 18 minutes light with water spray, or continuous light for indoor-use materials per ASTM D4459. Exposure duration is defined by total radiant exposure in kJ/m² at 340 nm or by elapsed hours.

Fluorescent UV Condensation Exposure

Fluorescent UV apparatus per ISO 4892-3, ASTM G154, and GB/T 16422.3 emphasizes the short-wave UV portion of sunlight, making it a severe and economical screening method for photodegradation. A common cycle uses UVA-340 lamps at 0.89 W/m² at 340 nm for 8 hours at 60 °C black panel temperature, alternating with 4 hours of condensation at 50 °C. This method is particularly effective at revealing yellowing tendencies in unstabilized polyolefins and paperboard.

Thermal and Humidity Aging

Long-term warehouse and distribution simulation employs forced-ventilation air ovens per ASTM D3045 and related heat-aging practices, typically at 40 °C to 80 °C, alone or combined with elevated humidity in damp-heat cycles. Thermal aging isolates thermo-oxidative yellowing of the substrate and coating from photodegradation and is essential for products stored in closed cartons or shipping containers.

Instrumental Color Difference Measurement

After exposure, specimens are reconditioned to the standard atmosphere, and color is re-measured at the previously marked positions. Color differences are calculated per ASTM D2244 and ISO 11664, reporting ΔL*, Δa*, Δb*, and ΔE*ab; where perceptibility judgments matter, CIEDE2000 ΔE00 is calculated. Yellowness and whiteness indices are computed per ASTM E313. Gloss is measured per ASTM D523 where relevant. Reports include exposure standard, cycle, radiant exposure or duration, black panel temperature, and the mean and range of replicate results.

Visual Assessment and Grey Scale Rating

Trained observers compare exposed and unexposed specimens side by side in a standardized viewing booth under D65 illumination in accordance with ASTM D1729. Change in color is assigned a grey scale rating from 1 (severe change) to 5 (no change) per ISO 105-A02. Visual ratings corroborate instrumental data and capture appearance effects that a single geometrical measurement may miss, such as non-uniform fading across printed graphics.

Applications

Packaging aging color change determination supports material qualification, supplier comparisons, and regulatory documentation across every major packaging end market:

• Food and beverage packaging: validating UV stability of bottles, caps, sleeves, and printed flexible laminates for window-display and outdoor vending exposure
• Pharmaceutical and healthcare packaging: demonstrating color stability of blister foils, labels, and printed primary packaging supporting photostability and shelf-life studies
• Cosmetics and personal care packaging: protecting premium brand colors on jars, tubes, and airless bottles where even small shade drift is commercially unacceptable
• Consumer goods and electronics packaging: qualifying cartons, sleeves, and thermoformed trays for extended retail and warehouse storage
• Material and formulation development: ranking UV absorbers, hindered amine light stabilizers, pigments, and ink binders; supporting quality-control release and incoming inspection specifications
• Failure analysis: diagnosing discoloration field complaints and differentiating light, heat, and contamination-induced mechanisms

Typical acceptance criteria are agreed between brand owner and supplier; common industrial thresholds are ΔE*ab ≤ 1.0 for premium cosmetic and brand-critical colors, ΔE*ab ≤ 2.0 for general consumer packaging, and a grey scale rating of 4 or better after the specified radiant exposure.

FAQ

What does ΔE actually measure?

ΔE is a single number representing the total distance between two colors in CIELAB space. A ΔE*ab of approximately 1.0 is a just-noticeable difference to a trained observer under good viewing conditions, while values above 2.0 to 3.0 are clearly visible to most consumers.

Which aging method should be chosen: xenon arc or fluorescent UV?

Xenon arc exposure per ISO 4892-2 best reproduces full-spectrum daylight and is preferred when results must correlate with real retail or outdoor display. Fluorescent UV per ISO 4892-3 is faster and more severe for short-wavelength UV effects and is widely used for screening and material ranking. Many development programs run both to separate spectral effects.

How long should the aging exposure be?

Duration is defined by the product's expected life and the chosen standard cycle, expressed in hours or total radiant exposure at 340 nm. Common screening points are 100, 250, 500, and 1000 hours, with measurement intervals that allow the color change curve versus dose to be plotted.

Can transparent films and printed labels be tested accurately?

Yes. Transparent films are measured over standardized white and black backings so that transmission-related changes are quantified reproducibly, and printed labels are tested with both solid ink patches and substrate-only areas so that ink colorfastness and substrate yellowing can be reported separately.

Why is a grey scale rating used if ΔE is already measured?

The instrumental ΔE is objective and traceable, while the grey scale rating per ISO 105-A02 expresses severity in a form widely referenced in print and textile supply-chain specifications. Reporting both gives a complete picture: numbers for specification compliance and a graded rating for contractual agreement.

What sample information should be provided for testing?

Submit representative production samples with material and pigment specifications, intended use and exposure environment, the applicable standard if already specified, and any acceptance limits. Accredited third-party laboratories can then recommend the most appropriate exposure cycle, measurement geometry, and reporting format for the application.