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D391-94 – Standard Test Method Technical Guide
🧪 Scope and Composition of D391-94
ASTM D391-94 (Reapproved 2000) provides the standard specification for Creosote-Coal Tar Solution used in the preservative treatment of wood. The standard mandates that the solution must be a pure coal tar product derived entirely from tar produced by the carbonization of bituminous coal. It specifically defines the material as either a coal tar distillate or a homogeneous solution of coal tar in coal tar distillate, ensuring a consistent and effective wood preservative base.
This specification covers four primary grades—Grades A, B, and C, as well as a specialized Marine Grade formulation for coastal water applications. The standard’s technical requirements closely align with the American Wood-Preservers’ Association (AWPA) Standards P2-68 and P12-68, ensuring broad industry applicability and historical continuity.
✅ Key Note: The standard is maintained by ASTM Committee D-7 on Wood and its Subcommittee D07.06, highlighting its critical role in the wood preservation industry.
🛠️ Sampling and Test Methods
To ensure strict compliance, Section 4 of D391-94 prescribes a comprehensive set of analytical methods. These standardized procedures characterize the physical and chemical properties of the creosote-coal tar solution. The material must be sampled in accordance with Test Methods D 38 prior to testing.
| 🟦 Property | 📋 Referenced Method | 🎯 Analytical Focus |
|---|---|---|
| Sampling | D 38 | Preservative sampling prior to testing |
| Water Content | D 370 (or D 95) | Quantification of water via distillation |
| Xylene Insolubles | D 367 | Determination of insoluble matter |
| Specific Gravity | D 368 | Overall density measurement |
| Distillation | D 246 | Boiling point fraction distribution |
| Sp. Gravity of Fractions | D 369 | Density of specific distillate fractions |
| Coke Residue | D 168 | Residual carbon content after heating |
| Volume/Sp. Gr. Correction | D 347 | Tables for temperature correction factors |
💡 Technical Tip: The selection of Test Method D 370 for water content can eliminate interference from water-soluble components, while D 95 offers a standard distillation alternative. The choice should be dictated by the specific characteristics of the sample lot.
📊 Key Properties and Grade Conformance
While the standard references specific test procedures, the pass/fail criteria are strictly based on the composition and property table (Table 1) within the standard. The key properties evaluated for grade conformance include the distillation range, water content, specific gravity, xylene-insoluble matter, and coke residue. Each grade (A, B, C, and Marine) has a defined limit for these parameters to ensure the preservative performs as intended in service.
| ⚖️ Composition Element | 📜 D391 Requirement | 🔗 Relevant Test Method |
|---|---|---|
| Base Material | Pure coal tar product from bituminous coal | Composition (Sec. 3) |
| Distillation Profile | Meets specified grade table limits (A, B, C, Marine) | D 246 |
| Specific Gravity | Conforms to grade-specific limits | D 368 |
| Water Content | Maximum specified per grade | D 370 / D 95 |
| Xylene Insolubles | Maximum specified per grade | D 367 |
| Coke Residue | Maximum specified per grade | D 168 |
❓ Frequently Asked Questions
🔍 What is the official designation of the standard for Creosote-Coal Tar Solution?
The standard is officially designated as ASTM D 391 – 94 (Reapproved 2000)e1. The “e1” superscript indicates an editorial change was made in March 2000.
💡 Which specific material is specified for the production of creosote-coal tar solution in D391?
The specification requires the solution to be a pure coal tar product derived entirely from tar produced by the carbonization of bituminous coal.
⚡ Can I use any test method for determining water content in the solution?
The standard designates Test Method D 370 as the primary method, but Test Method D 95 is explicitly listed as an alternative in Section 4.1.2.
📌 Is this ASTM standard aligned with other industry benchmark specifications?
Yes, the specification notes in its footnotes that it is essentially the same as the American Wood-Preservers’ Association (AWPA) Standards P2-68 and P12-68 for the respective grades, ensuring harmonization across the wood treating industry.