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D4414-95 – Standard Test Method Technical Guide
📏 Scope, Significance, and Applications
This practice describes the use of thin rigid metal notched gages for measuring the wet film thickness of organic coatings. These measurements are approximate but essential for controlling dry film thickness. The standard includes two procedures for different gage types and applications.
Notched gage measurements are neither accurate nor sensitive, but they are useful for articles where precise methods are not practical. Wet film thickness measurements help ensure coatings meet specifications, with a direct relationship to dry film thickness determined by volatile content.
⚠️ Notched gage measurements are approximate and should not be used for critical precision requirements.
⚙️ Measurement Procedures
Procedure A: Using a square or rectangular gage with notched sides, push perpendicularly into the wet film. Thickness ranges from 3 to 2000 µm (0.5 to 80 mils). Applicable to flat substrates and articles where end tabs can rest in the same plane.
Procedure B: Using a circular gage with spaced notches, roll perpendicularly across the film. Thickness ranges from 25 to 2500 µm (1 to 100 mils). Applicable to flat substrates and various complex shapes.
| 🟦 Procedure | 📏 Gage Type | 📐 Thickness Range (µm) | 🎯 Thickness Range (mils) | ⚡ Applicability |
|---|---|---|---|---|
| A | Square or rectangular | 3 to 2000 | 0.5 to 80 | Flat substrates and complex shapes with same plane for end tabs |
| B | Circular | 25 to 2500 | 1 to 100 | Flat substrates and various complex shapes |
💡 Use a clean gage and apply perpendicularly to the wet film. Avoid tilting to ensure accurate readings.
❓ Frequently Asked Questions
🔍 What is a notch gage?
A notch gage is a thin rigid metal tool with notches of varying depths. It is used to estimate wet film thickness by noting which notches become wetted when the gage is pressed into the coating.
💡 How is wet film thickness determined with a notch gage?
The gage is pushed or rolled into the wet film, then removed. The thickness is between the clearance of the deepest wetted notch and the next deeper notch that remains dry.
⚡ What are the thickness ranges for Procedures A and B?
Procedure A covers 3 to 2000 µm (0.5 to 80 mils), while Procedure B covers 25 to 2500 µm (1 to 100 mils).
📌 Can notch gages be used on curved or irregular surfaces?
Yes, particularly circular gages (Procedure B) are designed for use on objects of various sizes and complex shapes.