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D6073-08 – Standard Test Method Technical Guide
🧪 Scope and Principle of the Setting Test
This test method, designated D6073, describes the procedure for determining the relative setting speed of heatset printing inks using a forced hot air oven and print delivery system. It is applicable to printing inks intended for heat drying where a suitable reference standard is available. The test specifies the direct letterpress mode using a flatbed printing apparatus with a constant depth printing gage (in accordance with Practice D6846). This mode is chosen specifically because the higher ink film thicknesses it produces tend to amplify subtle differences in ink setting speed between the test sample and the standard.
⚙️ Procedure, Settings, and Equipment
A laboratory print is prepared containing both the test sample and a standard ink. The freshly prepared print is immediately subjected to forced hot air in the tester. The equipment is initiated at standard baseline conditions to establish a comparative framework, as detailed in the table below.
| 🟦 Parameter | 📏 Standard Setting | 🎯 SI Equivalent |
|---|---|---|
| Forced Air Oven Temperature | 350 °F | 177 °C |
| Belt Speed | 30 fpm | 0.15 m/s |
| Printing Mode | Direct Letterpress | Constant Gage Depth |
After thermal exposure, the print is cooled, overlaid with a clean sheet of stock, and passed through the printing apparatus to examine for setoff. This process is systematically repeated at different belt speeds or temperatures until either the test sample or the standard exhibits setoff while the other does not, confirming a relative difference.
📊 Interpretation and Significance of Results
The relative setting speed is determined by comparing the setoff behavior of the two inks. This method is directly useful for specification acceptance between a supplier and a customer, even though it does not exactly replicate a full production press environment. The evaluation criteria are summarized below.
| 🟦 Test Observation | 📐 Relative Setting Conclusion |
|---|---|
| Test sample shows setoff; Standard does not. | The sample sets slower than the standard. |
| Standard shows setoff; Test sample does not. | The sample sets faster than the standard. |
| Both or neither show setoff. | The setting speeds are considered equal under the tested conditions. |
📐 Unit Precedence: The standard expressly states that the values stated in inch-pound units are to be regarded as the standard. The metric equivalents provided in parentheses are mathematical conversions for information only and are not standard values.
💡 Reference Standard Validity: This test method relies entirely on the availability of a suitable reference standard for comparison. The stability and characterization of this standard ink are critical for achieving meaningful and reproducible relative results.
❓ Frequently Asked Questions
🔍 Why is the direct letterpress mode used instead of the typical offset process?
While heatset inks are frequently printed using the offset process, the direct letterpress mode generates a higher ink film thickness. This amplification of the ink film makes subtle differences in setting speed between the sample and the standard more readily observable.
💡 How does the standard define a “heatset printing ink”?
Per Section 3.1.1 of the standard, a heatset printing ink is defined as an ink typically containing aliphatic hydrocarbon solvents that evaporate at elevated temperatures.
⚡ What are the initial operating conditions for the forced hot air tester?
The tester is initially set to a temperature of 350°F (177°C) and a belt speed of 30 feet per minute (0.15 meters per second) as the starting point for the comparative analysis.
📌 What constitutes the “setoff” endpoint in this test?
After the print is cooled, it is overlaid with a clean sheet of stock and run through the printing apparatus. If ink transfers from the print to the clean sheet during this step, it is considered setoff. The test concludes when a differential in setoff is observed between the sample and standard.