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D1849-95 – Standard Test Method Technical Guide
📋 Scope and Normative References
ASTM D1849-95 (Reapproved 2019) provides a standard test method for evaluating the package stability of liquid paints, including both solvent-reducible and water-reducible types. The method assesses changes in consistency, skinning, settling, corrosion, and odor that occur when paint is stored at temperatures above 0°C (32°F). The standard utilizes several key referenced documents for specific testing equipment and procedures.
| 🛠️ Apparatus / Procedure | 📏 Specified Dimensions / Standard | 📄 ASTM Reference |
|---|---|---|
| Spatula | Mass: 45 ± 1 g, Blade: 120 mm × ~20 mm | D869 |
| Paint Brush | Width: 38 mm, Length Out: 63 mm, Thickness: 13 mm | — |
| Viscometer | Stormer-type with paddle rotor (Krebs Units) | D562 |
| Sampling | Duplicate samples in unopened containers (≤ 1 L) | D3925 |
⚙️ Test Procedure and Storage Conditions
Duplicate samples are obtained per Practice D3925. One sample is immediately evaluated for initial consistency (KU viscosity), skinning, settling, and general condition. The duplicate unopened samples are weighed to the nearest 1 g and stored undisturbed under specified conditions, typically for one month at 52 ± 1 °C (125 ± 2 °F). After storage, samples are reweighed to check for weight loss from faulty closure, then brought to the standard test temperature of 23 ± 2 °C (73 ± 3.5 °F).
The container is then opened and inspected. For containers ≤ 1 L (1 qt), the character of the settled layer is evaluated using the standard 45 g spatula technique described in Test Method D869. Visual checks for skinning, corrosion, pressure/vacuum, and olfactory checks for odors of “putrefaction, rancidity, or souring” are performed.
⚠️ Critical Limitation of Accelerated Testing: The standard explicitly warns that storage at 52°C (125°F) may not simply accelerate all changes occurring at 23°C (73°F). For water-borne paints, for instance, the elevated temperature inhibits the growth of putrefying bacteria, potentially masking biological spoilage that would occur under long-term ambient storage.
📊 Evaluated Properties and Reporting
The report for ASTM D1849 should document all observed changes. The primary properties evaluated are the change in consistency (measured in Krebs Units per D562), the degree of settling (rated soft, medium, or hard per D869), the presence of skinning or corrosion, and any weight loss. Observations of pressure, vacuum, and undesirable odors are also critical.
| 🎯 Property | 🔬 Evaluation Method | 📋 Criteria |
|---|---|---|
| Consistency Change | Stormer Viscometer (D562) | Change in Krebs Units (KU) |
| Settling | 45 g Spatula Test (D869) | Soft, Medium, or Hard Sediment |
| Closure Integrity | Weight Loss Measurement | Loss in grams |
| Biological Spoilage | Odor Inspection | Putrefaction, Rancidity, Souring |
💡 Tip for Reproducibility: The spatula for settling evaluation is highly regulated (45 ± 1 g, specific blade dimensions). Using an alternate spatula will invalidate the settling rating per D869. Ensure the test surface is impervious to the paint vehicle by using a properly varnished or lacquered paper chart.
❓ Frequently Asked Questions
🔍 What types of paint are within the scope of ASTM D1849?
The standard applies to liquid paints of either the solvent-reducible or water-reducible type stored at temperatures above 0°C (32°F).
💡 How does the accelerated storage condition correlate to real time?
Storage for one month at 52 ± 1 °C (125 ± 2 °F) is broadly correlated to simulate six months to one year of storage at 23 ± 2 °C (73 ± 3.5 °F), though the standard cautions that it is a simulation and not a perfect acceleration for all properties (e.g., biological growth).
⚡ What is the specific requirement for the spatula used in settling evaluation?
Per the referenced Method D869, the spatula must weigh 45 ± 1 g and have a square-ended blade 120 mm in length and approximately 20 mm in width. This precise specification is critical for standardizing the force applied during the evaluation.
📌 What defects does the test method focus on?
The method focuses on detecting changes in consistency (viscosity change), degree of pigment settling, skinning, corrosion of the container, weight loss (indicating faulty closure), and specific biological odors such as putrefaction, rancidity, or souring.