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D207-55 – Standard Test Method Technical Guide
🧪 Introduction and Scope
ASTM D207 – 55 (Reapproved 1995) e1 establishes the standard specification for Dry Bleached Lac, a material commonly referred to as “bone-dry,” “bac-dry,” or “kiln-dry” bleached lac. This standard, under the jurisdiction of ASTM Committee D01.33 on Polymers and Resins, defines the requirements for two distinct product grades: Regular and Refined.
The Refined grade is distinguished by an additional manufacturing process that removes practically all wax and insoluble matter. This results in a higher purity material suitable for applications demanding maximum clarity and consistency. An editorial note (e1) added in May 1995 inserted the Keywords section to aid in search and categorization.
📊 Key Material Property Requirements
Dry bleached lac must meet stringent limits for purity, moisture, and contaminants. The table below lists the exact maximum allowable percentages for both grades as specified in the standard.
| 🟦 Property | 📏 Regular Grade (max, %) | 📐 Refined Grade (max, %) |
|---|---|---|
| Matter Insoluble in Hot Solvents | 1.0 | 0.2 |
| Moisture | 6.0 | 6.0 |
| Wax | 5.5 | 0.2 |
| Matter Soluble in Water | 1.0 | 0.3 |
| Ash | 1.0 | 0.5 |
| Rosin | none | none |
| Copals | none | none |
The most significant differentiator between the two grades is the Wax content and Insoluble matter. While the Regular grade tolerates up to 5.5% wax, the Refined grade is capped at 0.2%. Both grades are strictly required to be entirely free from Rosin and Copals, ensuring a consistent, high-quality lac resin.
⚠️ Critical Note on Moisture: Despite the significant differences in purity levels, both the Regular and Refined grades share an identical maximum moisture limit of 6.0%. This makes moisture content a universal quality benchmark for all dry bleached lac.
⚙️ Test Methods and Compliance
Sampling and testing of dry bleached lac must be conducted strictly in accordance with ASTM D29 (Test Methods for Sampling and Testing Lac Resins). This ensures objective and reproducible results for all properties enumerated in the specification.
Originally adopted in 1925 and last revised in 1955, this standard represents a long-standing foundation for quality control in the lac industry.
💡 Technical Tip: When verifying the “none” requirement for Rosin and Copals, consult the specific test methods outlined in ASTM D29. The absence of these adulterants is critical for ensuring proper film formation and adhesion properties in downstream coating applications.
Keywords associated with this standard: lac; bleached lac; bone dry lac; refined lac.
❓ Frequently Asked Questions
🔍 What are the two grades of dry bleached lac defined in ASTM D207?
The standard defines Regular and Refined grades. The Refined grade has significantly lower wax and insoluble matter content.
💡 What is the maximum wax content for the Refined grade of dry bleached lac?
The Refined grade allows a maximum wax content of only 0.2%, compared to 5.5% for the Regular grade.
⚡ What is the maximum moisture content specified for dry bleached lac?
Both the Regular and Refined grades must conform to a maximum moisture content of 6.0%.
📌 Which standard must be referenced for testing dry bleached lac?
All testing must be performed according to ASTM D29, the Standard Test Methods for Sampling and Testing Lac Resins.