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D2482-97 – Standard Test Method Technical Guide
📐 Scope and Significance of D2482-97
ASTM D2482-97 (Reapproved 2007) defines the Wax Pick Method for determining the surface strength of uncoated and coated papers. This test measures resistance to picking, which is critical for printing, coating, and converting operations where transverse surface strength is required. The method is technically similar to TAPPI T 459 but carries specific ASTM apparatus and procedural requirements for adhesion testing.
⚠️ Critical Limitations: This standard explicitly excludes loosely felted papers (e.g., blotters, roofing felts) and coated papers containing thermoplastic resins. The molten wax forms an artificially strong bond with thermoplastic adhesives, yielding false low-strength values that do not correlate with actual press performance. For sheets containing latex or similar substances, Section 5.2.1 recommends using the actual printing medium instead.
| 🟦 Parameter | 📏 Specification |
|---|---|
| Standard Designation | D2482 – 97 (Reapproved 2007) |
| Applicable Materials | Uncoated and coated papers |
| Wax Series Range | 2A to 26A (hard-resin, non-oily) |
| Wax Stick Cross-Section | 18 x 18 mm (11/16 x 11/16 in.) |
| Standard Specimens | 10 units, 100 x 100 mm (4 x 4 in.) |
⚙️ Test Apparatus and Procedure
The equipment is deliberately simple but precisely specified. A heating device (Bunsen burner, alcohol lamp, propane torch, or electric element) melts the calibrated wax stick. The molten wax is poured into the 30 mm diameter hole of a standardized wooden block measuring approximately 90 x 40 x 10 mm. The work surface must be a poor heat conductor, specifically wood; glass, metal, or artificially cooled surfaces are explicitly prohibited as they alter the cooling rate and bond formation of the wax.
💡 Best Practice: Condition all test specimens strictly in accordance with Practice D685 before testing to ensure standardized moisture content and temperature equilibrium. Apply the wax perpendicular to the surface, allow it to set fully, and lift the block straight up without twisting to achieve a consistent pick.
| 🎯 Component | 📐 Dimension / Value |
|---|---|
| Wooden Block Overall Size | 90 x 40 x 10 mm (3.5 x 1.5 x 0.375 in.) |
| Test Hole Diameter | 30 mm (1.25 in.) |
| Hole Edge Distance (from end) | 3 mm (0.125 in.) |
| Heating Device Types | Bunsen burner, alcohol lamp, propane torch, or electric element |
| Work Surface Requirement | Smooth, hard, poor conductor (wood only) |
📊 Interpreting the Wax Pick Number
According to Section 4.1, the highest-numbered wax in the series (2A through 26A) that does not disturb the surface of the paper is the numerical rating of the pick. The test provides comparative values rather than absolute physical constants. Standard Section 5.1 strongly emphasizes that test results should be correlated with actual performance during the subsequent coating, converting, printing, or packaging operation to ensure practical relevance for the end-use application.
❓ Frequently Asked Questions
🔍 What does the Wax Pick Number indicate?
The numerical rating represents the highest-numbered calibrated wax in the 2A to 26A series that can be pulled from the paper surface without causing visible picking, delamination, or fiber disturbance. A higher number indicates greater surface strength.
💡 Why is the test unreliable for coated papers containing latex?
As detailed in Section 5.2, the molten wax forms an abnormally strong bond with thermoplastic resins in the coating adhesive. This causes the paper to appear weaker than it actually is in a printing press environment, making the standard wax test invalid for these specific materials without modification.
⚡ Is this test applicable to loosely felted papers?
No. Section 1.1 explicitly excludes loosely felted papers such as blotters or roofing felts, which lack the cohesive surface structure required for a valid wax-pull evaluation.
📌 What conditioning and sampling standards apply?
Sampling must be performed in accordance with Practice D585. Specimens must be conditioned according to Practice D685 for Paper and Paper Products. Terminology definitions are governed by Terminology D1968 and the Dictionary of Paper.