Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D4361-10 – Standard Test Method Technical Guide
The ASTM D4361-10 standard specifies a precise methodology for evaluating the rheological behavior of paste-type printing inks and vehicles. Using a three-roller tackmeter, this test method quantifies apparent tack, a critical parameter that correlates with an ink’s performance on high-speed printing presses.
📐 Test Scope and Instrument Geometry
This standard is strictly applicable to paste-type printing inks and vehicles that remain essentially nonvolatile under ordinary room conditions. A key prerequisite is that the elastomer covering the tackmeter rollers must be chemically resistant to the specific ink or vehicle being tested. The method explicitly addresses instruments of two distinct configurations—Geometry A and Geometry B—which may yield different numerical values for the same fluid.
📌 Critical Insight: Apparent tack values are not absolute physical constants. They are heavily dependent on the specific instrument geometry, calibration status, zero accuracy, and operating conditions. Results generated on different manufacturers’ tackmeters or different geometries should not be directly compared without a correlation study.
| 🟦 Parameter | 📏 Specification |
|---|---|
| Test Material | Paste-type printing inks & nonvolatile vehicles |
| Instrument Type | Three-roller tackmeter (Geometry A or B) |
| Roller Material | Chemically resistant elastomer |
| Unit System | SI units |
| Application Scope | Quality control, formulation, and production simulation |
⚙️ Operational Principle and Critical Conditions
A thin film of the test fluid is applied to the three-roller distribution system, which operates at speeds comparable to those in production printing press roller trains. The frictional torque generated by the drag forces within the splitting fluid film provides the measured apparent tack value. The standard procedure is designed to yield a single value at a highly specific set of instrument conditions.
| 🎯 Variable | ⚡ Influence on Tack Measurement |
|---|---|
| Separation Velocity | Directly alters the force required to split the film |
| Splitting Area / Roller Force | Changes the distribution and stress on the fluid |
| Film Thickness | Varies the volume and rheological stress in the nip |
| Temperature / Time | Changes viscosity and internal cohesion of the fluid |
| Elastomer Condition | Age, chemical attack, and mechanical flaws alter friction |
💡 Good Practice: Because readings are sensitive to the condition of the rollers, always clean the elastomer rollers immediately after testing with an appropriate solvent. Regularly calibrate the tackmeter and verify zero accuracy before each test sequence to ensure reliable results.
📊 Key Rheological Phenomena: Flying and Misting
The standard provides specific definitions for related ink behaviors observed during high-speed roller distribution. Flying is the tendency of the ink to be ejected as large globules, which is generally most severe during rapid roller acceleration. Misting is the tendency to be ejected as a fine aerosol, which is typically most severe at high operating speeds with fluids that form long filaments.
❓ Frequently Asked Questions
🔍 What is the primary distinction between “tack” and “apparent tack”?
“Tack” is defined as the fundamental rheological parameter representing the force required to split a thin fluid film between rapidly separating surfaces. Because this force varies significantly with operating conditions, the standard defines “apparent tack” as the specific numerical reading obtained at a prescribed set of conditions.
💡 Why does the standard differentiate between Geometry A and Geometry B?
The standard acknowledges that three-roller tackmeters are built with different physical configurations. Stating the geometry is crucial because the apparent tack value reported is a function of the instrument’s design. Readings can vary between suppliers and geometries, making it essential to identify the specific geometry used in the report.
⚡ What factors cause tack readings to vary during a single test?
Tack is not a fixed number. According to the standard, it varies primarily with separation velocity, splitting area, force applied by the measuring roller, and film thickness. Additionally, changes in rheological properties due to heat buildup, time under shear, and interactions with the roller surfaces will cause the reading to drift.
📌 How are “flying” and “misting” differentiated in this standard?
Flying describes the ejection of large ink globules and is most common during rapid acceleration. Misting describes the ejection of a fine aerosol and is most common at sustained high operating speeds, particularly with fluids that form long, cohesive filaments.