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D3891-23 – Standard Test Method Technical Guide
🧪 Significance and Use
This practice provides standardized procedures for preparing glass panels to ensure uniformity in testing paint, varnish, lacquer, conversion coatings, and related products. The methods described are designed to yield clean, consistent surfaces for reliable test results.
🪟 Glass Types and Specifications
The following glass types may be specified depending on the test requirements:
| 🪟 Glass Type | 📏 Description | 📐 Thickness | 🎯 Notes |
|---|---|---|---|
| Window Glass (Float Glass) | Plain, free of irregularities; produced by floating on molten tin | Standard window thickness | Tin side and air side have different adhesion characteristics. Use UV-A light to distinguish. |
| Clear Plate Glass | Transparent plate glass | Not less than 5 mm (0.16 in.) | For applications requiring thicker substrate. |
| Plate Glass (Ground) | Ground uniformly on one side with 1F carborundum | Varies | Provides a rough surface for improved adhesion. |
| Black Structural Glass | Polished to a smooth, high-gloss surface on one side | Varies | For testing with dark backgrounds. |
| White Structural Glass | Polished to a smooth, high-gloss surface on one side | Varies | For testing with light backgrounds. |
🧹 Method of Preparation
For new panels, clean using a lintless cloth with a solvent mixture of equal volumes of VM&P naphtha and xylene, or 3 parts VM&P naphtha to 1 part 2-methoxypropanol, or water. Wash off soluble and adhering soil, then flush with clean solvent. Dry at room temperature or force dry at up to 150 °C (302 °F). Allow to cool to room temperature before use.
💡 Tip: For float glass, the tin side may affect chemical analysis. Use UV-A light to identify the appropriate side for your test.
⚠️ Safety: Ensure adequate ventilation when using organic solvents; follow all safety guidelines for handling chemicals.
❓ Frequently Asked Questions
🔍 Q: What is the recommended way to clean glass panels?
A: Use a lintless cloth with a solvent mixture of VM&P naphtha and xylene (1:1 by volume) or VM&P naphtha and 2-methoxypropanol (3:1), or water, followed by flushing with clean solvent and drying.
💡 Q: How can I identify the tin side of float glass?
A: Expose the glass to UV-A light. The air side appears clear, while the tin side appears frosted.
⚡ Q: What is the maximum drying temperature for prepared panels?
A: Force drying should not exceed 150 °C (302 °F) to avoid glass damage or contamination.
📌 Q: What type of water should be used for cleaning?
A: Use reagent water conforming to Type IV of Specification D1193.