ASTM D4086 Standard Practice for Visual Evaluation of Metamerism

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ASTM D4086 testing is useful for the manufacturer, coating producers, pigment and dye manufacturers, textile producers, plastics producers, color-matching specialists, and quality control personnel, among others, who are evaluating visual color consistency. The evaluation consists of visually comparing the test specimen to a reference in controlled conditions and then determining if the apparent relationship of the two samples has changed when the viewing condition changes. Observational practice is dependent on visual perception, and therefore, selection and training of appropriate observers is crucial for obtaining consistent results. ASTM E1499 explicitly identifies metamerism evaluation (according to D4086) as a task for trained visual-sensory observers. Evaluation by a professional using ASTM D4086 can be used to determine undesirable metamerism, to quantify the size, and to record visual metamerism behavior for product development, quality control, supplier assessment, and color acceptance.

• Evaluation Type: Visual evaluation of metamerism.
• Metamerism Covered: Illuminant metamerism and observer metamerism.
• Property Evaluated: Presence and apparent magnitude of a metameric color difference.
• Color Comparison: Visual comparison of a reference and test specimen under applicable viewing conditions.
• Observer: Human visual-sensory observer performing the evaluation.
• Gonioapparent Samples: Samples whose appearance changes with illumination or viewing geometry are outside the scope.
• Instrumental Indices: The practice does not calculate metamerism indices from instrumental spectral measurements.
• Safety: Users are responsible for establishing appropriate safety, health, and environmental practices applicable to the evaluation.

What are the uses of ASTM D4086 testing?

ASTM D4086 provides a practical way to determine whether an apparent color match remains visually consistent when viewing conditions change. This is especially useful when different pigments, dyes, or colorant systems produce a nominally matching color. The practice can be used in both field and laboratory environments where suitable visual conditions can be established. ASTM notes that purchasers may require nonmetameric color matches, while limitations on metamerism may be established where completely nonmetameric matches are impractical. Common uses include:

• Color Matching: Evaluate the visual relationship between a reference and test color.
• Quality Control: Identify undesirable metamerism in production materials.
• Pigment and Dye Evaluation: Compare color matches produced using different colorants.
• Coating Evaluation: Examine color consistency between coated surfaces.
• Textile Evaluation: Assess color matches between textile materials.
• Plastic Product Evaluation: Examine colored plastic parts and plaques.
• Supplier Evaluation: Compare supplied materials with approved color references.
• Product Development: Support colorant and formulation selection.
• Color Specification: Evaluate compliance with agreed limitations on metamerism.
• Field Inspection: Visually assess color relationships under appropriate illumination.

Which Materials Can Be Tested According to ASTM D4086?

ASTM D4086 is applicable to colored specimens that can be visually compared with a reference specimen. It is not limited to one specific material type; its suitability depends primarily on whether the specimens can be presented under appropriate visual conditions and whether their color relationship can be meaningfully assessed. Materials and products that may be evaluated include:

• Painted panels and coated surfaces
• Plastic plaques and colored plastic components
• Textile and fabric specimens
• Pigmented polymer materials
• Colored coatings and finishes
• Products containing pigments or dyes
• Color-matched production samples
• Reference and production specimens manufactured using different colorant systems

Why is ASTM D4086 Testing Important?

A reference and production specimen may appear to match under one illuminant but show a visible difference under another. ASTM D4086 provides a standardized visual approach for identifying this type of metameric behavior and estimating its magnitude. The practice is important for products where consistent appearance is required across different lighting conditions or where different colorant systems are used to reproduce the same target color. It can help manufacturers identify color matches that may not remain visually consistent in actual use. ASTM D4086 can also complement instrumental color evaluation. ASTM D2244 indicates that when specimens are suspected of being metameric, D4086 can be used to visually verify the instrumental evaluation.

ASTM D4086 Testing Process and Data Collection

Technicians or color specialists first identify the reference and test specimens and verify that the specimens are clean, representative, and suitable for visual comparison. The specimens are positioned appropriately and presented under controlled viewing conditions so that the observer can evaluate their relative appearance. The observer compares the reference and test specimen under the applicable illumination and determines whether the apparent color relationship changes. The evaluation focuses on visual metameric behavior rather than calculating an instrumental metamerism index. ASTM D4086 does not provide a method for computing metamerism indices based on instrumental spectral characteristics. The technician records specimen identification, reference information, material or product description, viewing arrangement, illumination information, observer information where applicable, and relevant visual observations. The analyst or qualified color evaluator documents whether metamerism is detected and estimates the magnitude of the metameric color difference. 

Common Challenges and Troubleshooting

Inconsistent illumination can make visual comparisons difficult and may produce different observations between evaluations. The viewing environment and light source should therefore be controlled and maintained consistently. Observer variability can influence visual assessments. ASTM E1499 provides guidance for selecting, evaluating, and training visual-sensory observers, and specifically identifies D4086 metamerism evaluation as an applicable visual task.

• Metamerism results are interpreted according to the ASTM D4086 visual evaluation procedure. The practice addresses illuminant metamerism and observer metamerism, while gonioapparent samples and instrumental metamerism-index calculations are outside its scope.
• The technician records specimen identification, reference and test specimen descriptions, surface condition, viewing arrangement, illumination information, observer information, and other relevant evaluation conditions.
• The analyst or qualified color evaluator documents whether metamerism is observed, describes the change in apparent color relationship, estimates the magnitude of the metameric color difference, and records relevant visual observations.
• The report contains the reference and test specimen identification, material or product description, viewing conditions, illumination conditions, observer information where applicable, visual observations, metamerism determination, estimated magnitude, and applicable limitations.
• ASTM D4086 does not produce a universal numerical test result or SI unit. The principal result is a visual determination and estimation of the magnitude of a metameric color difference. Instrumental color coordinates or calculated metamerism indices, when required, should be reported separately using the applicable instrumental method.
• When technicians and analysts provide ASTM D4086 evaluations, the following factors can be used to ensure that they are provided in a consistent and comparable manner: Standardized presentation of specimens, controlled illumination, consistent viewing conditions, trained observers, appropriate reference materials, systematic documentation.

Link to ASTM D4086