Emulsion thickness building beyond the mesh threads (substrate side).
Angle and polyurethane durometer controlling ink deposit.
Fixed grid variable size (AM) vs random distribution fixed size (FM).
| Technical Term | Process Definition | Target Parameter / Unit | Direct Pressroom Impact |
|---|---|---|---|
| EOM (Emulsion Over Mesh) | Percentage of dry emulsion thickness built beyond the substrate side of the mesh threads. | 10% - 20% (Measured in µm with thickness gauge) | Low EOM causes saw-toothing and fuzzy edges; excessive EOM increases ink consumption and drying time. |
| Squeegee Durometer (Shore A) | Hardness rating of the polyurethane blade used to shear ink through the mesh. | 60 ShA (Soft) - 80 ShA (Hard) | Soft blades deposit thicker ink layers; hard blades yield sharp detail and control dot gain. |
| Off-Contact Distance | The gap set between the bottom of the stretched screen and the substrate surface. | 1.5 mm - 4.0 mm (dependent on frame size) | Ensures clean screen snap-off immediately behind the squeegee stroke, preventing smearing. |
| Mesh Tension | The mechanical force applied across the screen mesh, measured using a Newton meter. | Newton/cm (N/cm) (e.g., 18-25 N/cm) | Low tension leads to registration loss, poor snap-off, and requires excessive squeegee pressure. |
| LPI (Lines Per Inch) | Frequency of halftone dots per inch used in raster image processing. | 45 - 65 LPI (Recommended Mesh 120-140 threads/cm) | Defines print resolution. The industry rule requires mesh count ≥ 4.5x line count. |
| Thixotropy | The property of screen printing inks to become less viscous when sheared (stirred or squeegeed). | Pascal-seconds (Pa·s) / Viscometer | A proper thixotropic ink flows smooth during pressing but stays firm on the screen without dripping. |
| TDS (Technical Data Sheet) | Manufacturer specifications defining mesh limits, cure temperatures, and chemical compatibility. | Compliance Document | Prevents wash-fastness failures and chemical degradation of ink binders. |
| Visual Defect | Root Chemical/Physical Cause | Corrective Shop Action |
|---|---|---|
| Moiré Pattern (Interference) | Halftone screen angle geometrically clashing with the woven mesh threads. | Rotate AM screen angles by 7.5°/15° or convert film output to FM stochastic screening. |
| Saw-Toothing (Jagged Edges) | EOM below 5% or under-exposure during UV stencil burning. | Increase emulsion coating passes on print side (e.g., 1:2 coat) and perform exposure calculator test. |
| Shadow Dot Gain (Detail Loss) | Excessive squeegee pressure or soft blade (<65 ShA) crushing halftone dots. | Increase blade hardness to 75/80 ShA, lower squeegee pressure, and verify off-contact. |
In many print shops, I hear operators talking about "thick ink" or "loose mesh" without measuring a single thing. Modern screen printing is physics and chemistry: EOM is measured in microns with a digital gauge, not guessed by eye. If you don't know the difference between 65 Shore and 80 Shore, or if you're using a rounded blade for 55 LPI halftones, you're relying on luck and wasting money on scrapped garments.
Learn to use exact terminology at the press-check: when a client complains about a "heavy hand," the issue isn't the ink quality—it's an excessive EOM or the wrong mesh selection laying down three times the required deposit.