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D3210-95 – Standard Test Method Technical Guide
ASTM D3210-95 (Reapproved 2023) establishes a standardized procedure for comparing the colors of films deposited from water-emulsion floor polishes. By utilizing a tristimulus colorimeter, this test method quantifies film color in terms of a Whiteness Index (WI), offering an objective measure of potential discoloration on flooring substrates.
📖 Scope and Significance of the Whiteness Index
This test method covers the comparison of colors of films (or solids) deposited from emulsified particles in water-emulsion floor polishes. The measurements are based on luminous reflectance readings obtained from a tristimulus colorimeter, such as the Hunter Color Difference Meter, which directly provides L, a, and b color scale values.
The color measurement is expressed as the Whiteness Index (WI), defined by the equation WI = L – 3b. In this context, L represents lightness (100 for perfect white, zero for black), and b measures yellowness (positive) or blueness (negative). The Whiteness Index is particularly useful for predicting the potential discoloring effect of polish films and for specification purposes when comparing samples against a standard polish.
💡 Tip: The Whiteness Index (WI) is derived from measurements on exaggerated or heavy dried polish films created by saturating white filter paper. This technique magnifies color differences between samples for more accurate detection and comparison.
✅ Standard Status: Originally approved in 1973, D3210-95 was reapproved in 2023 without revision, confirming its continued validity and consistent use within the industry for evaluating the color of floor polish films.
⚙️ Apparatus and Test Procedure
The following specific apparatus is required by the standard:
- Tristimulus Colorimeter: An instrument giving reflectance readings convertible to L, a, b color scale values, or reading them directly.
- Filter Paper: Standard medium flow rate, cut into precise strips of 76.2 mm by 152.4 mm (3 in. by 6 in.).
- Spring Clamps: Two spring clamps, approximately 76 mm (3 in.) wide, for handling the saturated paper strips.
The test procedure involves saturating the filter paper strips with the polish sample to create an exaggerated dry film. Reflectance measurements are then performed on these prepared strips using the colorimeter.
📊 Key Calculations and Measured Properties
The fundamental calculation in this standard is the Whiteness Index. While modern tristimulus instruments often read L and b directly, the standard provides conversion factors for instruments that read in X, Y, Z tristimulus units. The core measured properties are dimensionless indices on the Hunter color scale.
| 🟦 Equation | 📏 Description |
|---|---|
| WI = L – 3b | Whiteness Index from direct L and b readings |
| L = 10√Y | Lightness converted from tristimulus Y-value |
| b = 7.0(Y – 0.847Z) / √Y | Yellowness/Blueness converted from Y and Z values |
| 📐 Equipment | ⚡ Specification |
|---|---|
| Colorimeter Type | Tristimulus (e.g. Hunter Color Difference Meter) |
| Filter Paper Size | 76.2 mm × 152.4 mm (3 in. × 6 in.) |
| Spring Clamp Width | Approx. 76 mm (3 in.) |
A higher Whiteness Index indicates a brighter, less yellow film. The L value is a direct measure of light reflectance (lightness), while the b value quantifies the balance between yellow and blue color cast in the deposited polish film.
❓ Frequently Asked Questions
🔍 What is the primary purpose of ASTM D3210-95?
This standard provides a test method for comparing the colors of films deposited from water-emulsion floor polishes. It translates visual color appraisal into an objective numerical value known as the Whiteness Index (WI).
💡 How is the Whiteness Index (WI) calculated?
The Whiteness Index is calculated using the equation WI = L – 3b. L represents the lightness of the film (0 for black, 100 for perfect white), and b quantifies yellowness (positive) or blueness (negative).
⚡ What type of instrument is required for this test?
The method specifically requires a tristimulus colorimeter, such as the Hunter Color Difference Meter. This instrument provides the L, a, and b Hunter color scale values needed to compute the Whiteness Index.
📌 What specific dimensions are required for the test specimen?
The test apparatus specifies filter paper strips cut to a precise dimension of 76.2 mm by 152.4 mm (3 in. by 6 in.). Two spring clamps, approximately 76 mm (3 in.) wide, are required for handling the specimens.