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D4941-06 – Standard Test Method Technical Guide
📐 Scope and Significance of D4941
This standard practice specifically addresses the unique challenges of preparing uniform films of artists’ paste paints, which are typically nonflowing. The primary goal is to produce drawdowns suitable for critical visual and colorimetric evaluations such as tinting strength (Test Method D4838), color designation, transparency, and gloss measurement.
⚠️ Important Consideration: Artists’ tube paints have a paste consistency that makes the use of traditional film application methods difficult, especially for drying oil paints. The values stated in SI units are regarded as the standard.
⚙️ Drawdown Procedure and Key Terminology
Section 3 of the standard defines the critical equipment and materials. A drawdown bar is a metal applicator with a specified gap designed to deposit a wet paint film uniformly on a specified test panel. The deposited layer itself is known as a drawdown.
| 📏 Key Term | 📖 Definition from Section 3 |
|---|---|
| Drawdown | A layer of paint deposited on a substrate by use of a drawdown bar for the evaluation of paint characteristics. |
| Drawdown Bar | A metal applicator with a specified gap designed to deposit a wet paint film uniformly on a specified test panel (e.g., an opacity chart) or other substrate. |
The practice summary (Section 4) specifies that the paint is spread over the area of the test panel to be covered, and the bar is pulled down with pressure just sufficient to avoid lifting of the bar from the chart surface. Test panels are then allowed to dry in a dust-free environment.
🎯 Achieving Opaque Specimens
A common challenge outlined in Section 5.3 is that artists’ paints vary in transparency and drying time. Very transparent paints require such a thick film to produce complete hiding that drying times become excessively long or the specimen surface is blemished. This practice solves this by applying a series of thin films.
✅ Optimal Technique for Opacity: If complete hiding (opacity) is needed and not produced by a single paint film, the standard prescribes applying a second film at a 90° angle to the first. If required, additional layers may be applied using a narrower drawdown bar.
| 📊 Property Evaluated | 📜 Referenced Standard/Method |
|---|---|
| Relative Tinting Strength | Test Method D4838 |
| Colorimetric Measurement | Practice E1164 |
| Terminology | Terminology D16 |
❓ Frequently Asked Questions
🔍 What is a drawdown bar? It is a metal applicator with a specified gap designed to deposit a wet paint film uniformly on a specified test panel (e.g., an opacity chart). It is the primary tool used in this practice.
💡 Why are artists’ paste paints difficult to test? Artists’ tube paints have a paste consistency that makes the use of traditional film application methods difficult. They are nonflowing, which is very different from less viscous industrial paints.
⚡ How is complete hiding achieved for transparent paints? The standard recommends applying a second film at a 90° angle to the first if the initial film does not provide hiding. Additional layers can be applied using a narrower drawdown bar to avoid excessive drying times and surface defects.
📌 What is the scope of this standard? It covers the production of uniform films of artists’ tube paints and other nonflowing pigmented paints. It includes information on how to achieve opaque specimens from these paints.