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D1544-04 – Standard Test Method Technical Guide
📐 Scope and Significance
ASTM D1544-04 (Reapproved 2023) provides the standard test method for measuring the color of transparent liquids using the Gardner Color Scale. It is specifically designed for drying oils, varnishes, fatty acids, polymerized fatty acids, and resin solutions. A critical requirement for operators is normal color vision to ensure accurate visual matching. The standard mandates that values be reported in SI units and emphasizes adherence to established safety practices.
⚠️ User Vision Requirement
This method relies entirely on human visual perception. All personnel performing the comparison must have normal color vision to ensure reliable and reproducible results.
This method relies entirely on human visual perception. All personnel performing the comparison must have normal color vision to ensure reliable and reproducible results.
⚙️ Apparatus and Test Procedure
The apparatus consists of 18 numbered glass standards with defined color characteristics, clear glass tubes (10.65 mm internal diameter, approximately 114 mm external length), and a comparison apparatus. The comparison apparatus must strictly conform to several optical requirements: illumination must be CIE Illuminant C, the surrounding field must be black, and the specimen and standard must subtend a simultaneous visual angle of approximately 2° with minimal separation between them.
The procedure requires filling a glass tube with the liquid sample, filtering it if it appears cloudy, and then visually comparing it to the glass standards. The operator must match based on brightness and saturation while ignoring any differences in hue.
💡 Calibration Verification
Some glass standards in circulation no longer conform to the specified values. Always verify the calibration of your standards against the specifications in Table 1 before performing tests. A detailed verification procedure can be found in Appendix X1 of the full standard.
Some glass standards in circulation no longer conform to the specified values. Always verify the calibration of your standards against the specifications in Table 1 before performing tests. A detailed verification procedure can be found in Appendix X1 of the full standard.
📊 Results, Reporting, and Specifications
Results are reported as the number of the standard most closely matching the specimen. For higher precision between two colors, the report can include light or dark steps (e.g., between 5 and 6: 5, 5+, 6−, 6). The following table details the specific color characteristics for each of the 18 glass standards.
| 🟦 Gardner No. | 📏 CIE x | 📐 CIE y | 🎯 Dominant λ (nm) | ⚡ Purity (%) |
|---|---|---|---|---|
| 1 | 0.3177 | 0.3300 | 573 | 6 |
| 2 | 0.3233 | 0.3352 | 573 | 10 |
| 3 | 0.3290 | 0.3405 | 573 | 14 |
| 4 | 0.3350 | 0.3460 | 573 | 18 |
| 5 | 0.3412 | 0.3516 | 573 | 22 |
| 6 | 0.3476 | 0.3574 | 574 | 26 |
| 7 | 0.3543 | 0.3633 | 574 | 30 |
| 8 | 0.3612 | 0.3694 | 574 | 34 |
| 9 | 0.3684 | 0.3756 | 574 | 38 |
| 10 | 0.3758 | 0.3820 | 575 | 42 |
| 11 | 0.3835 | 0.3885 | 576 | 46 |
| 12 | 0.3915 | 0.3951 | 576 | 50 |
| 13 | 0.3998 | 0.4019 | 577 | 54 |
| 14 | 0.4084 | 0.4087 | 578 | 58 |
| 15 | 0.4174 | 0.4157 | 579 | 62 |
| 16 | 0.4267 | 0.4228 | 581 | 66 |
| 17 | 0.4364 | 0.4300 | 583 | 70 |
| 18 | 0.4465 | 0.4373 | 585 | 74 |
❓ Frequently Asked Questions
🔍 What specific materials are within the scope of D1544?
This test method applies explicitly to drying oils, varnishes, fatty acids, polymerized fatty acids, and resin solutions. Its applicability to other transparent liquids has not been formally tested by the responsible subcommittee.
💡 What illumination is required for the comparison apparatus?
The standard strictly requires CIE Illuminant C. The surrounding field must be black, and the specimen and standard must be viewed simultaneously at a visual angle of about 2°.
⚡ How are results reported when a sample falls between two standard colors?
For routine reporting, the closest matching number is used. For higher precision, the report can indicate if the sample is lighter or darker. For instance, between standard colors 5 and 6, the steps would be reported as 5, 5+, 6−, and 6.
📌 What are the required dimensions for the sample tube?
The standard calls for clear glass tubes with an inside diameter of 10.65 mm and an outside length of about 114 mm. Viscosity tubes described in Test Method D1545 are considered satisfactory.