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D267-82 – Standard Test Method Technical Guide
ASTM D267-82 (Reapproved 2020) provides the standard specification for gold bronze, pale gold bronze, and rich gold bronze powders used in decorative and protective coatings. These pigments, composed of finely polished metal flakes suspended in a lubricant, are designed to produce the characteristic “gold” effects in paints and industrial finishes. Originally adopted in 1926, the standard gained its current designation D267 in 1982 and received its most recent reaffirmation in 2020, confirming its ongoing relevance within the paint and coatings industry under ASTM Committee D01. This article highlights the core technical requirements of the standard, focusing on composition, performance testing, and quality assurance protocols.
📐 Composition and Physical Requirements
The standard mandates that gold bronze powder must be manufactured using entirely new ingot metals to ensure purity and consistent performance. The metal is processed into fine, polished flakes. To provide adequate leafing properties and ensure the flakes float to the surface to form a brilliant film, the powder must contain not less than 3% fatty or oily matter (polishing lubricant) by weight.
| 🟦 Parameter | 📏 Specification |
|---|---|
| Base Material | New ingot metals |
| Polishing Lubricant (Fatty/Oily Matter) | ≥ 3 % (for good leafing) |
| Residue on No. 100 (150 μm) Sieve | ≤ 0.2 % (using alcohol wash) |
| Mixing Ratio for Leafing Test | 3 to 4 lb/gal (370 to 475 g/L) |
⚠️ Critical Point: The residue retained on a No. 100 sieve must not exceed 0.2% when tested in accordance with ASTM D185. Exceeding this limit indicates unacceptable coarse particles in the pigment.
⚙️ Leafing Properties and Test Procedures
“Leafing” is the property of the bronze powder to form an apparently continuous, brilliant metallic film over the free surface of a suitable liquid vehicle within 1 minute after stirring ceases. The standard specifies a test mixture using a varnish/turpentine blend with a viscosity of 0.65 to 0.85 poises (B to C on the Gardner-Holdt scale). The spar varnish must conform to Federal Specification A-A-1800, and the turpentine to ASTM D13.
| 🎯 Criterion | ⚡ Requirement |
|---|---|
| Leafing Film Formation | Continuous brilliant film within 1 minute |
| Test Vehicle (Spar Varnish) | Conforms to Federal Spec A-A-1800 |
| Test Vehicle (Turpentine) | Conforms to ASTM D13 |
| Vehicle Viscosity | 0.65 – 0.85 poises (Gardner-Holdt B to C) |
| Powder Loading for Test | 3 to 4 lb powder per gallon of vehicle |
Additionally, the blended mixture must flow freely and produce a smooth, continuous coating consistent with the procedures in ASTM D480. The final shade and fineness of the powder must match a mutually agreed upon reference sample between the purchaser and the seller.
📊 Sampling and Quality Assurance
ASTM D267 outlines stringent sampling protocols. For any shipment, two random