Angular separation between dominant dark channels prevents optical moiré patterns.
Elliptical dots split midtone bridge connection points between 45% and 55% coverage.
Mechanical squeeze expands dot perimeter footprint upon fabric transfer.
| Color Channel | Standard Screen Angle | Dot Shape Profile | Recommended LPI Range | Target Mesh Count |
|---|---|---|---|---|
| Cyan (C) | 15° (or 105°) | Elliptical (Euclidean) | 45 - 65 LPI | 120-34 threads/cm (305-34 tpi) White |
| Magenta (M) | 75° (or 15°) | Elliptical (Euclidean) | 45 - 65 LPI | 120-34 threads/cm (305-34 tpi) White |
| Yellow (Y) | 0° (or 90°) | Elliptical / Round | 45 - 65 LPI | 120-34 threads/cm (305-34 tpi) Yellow |
| Key / Black (K) | 45° | Elliptical (Euclidean) | 45 - 65 LPI | 120-34 threads/cm (305-34 tpi) Yellow |
| Operating Parameter | Optimal Target | Tolerance | Impact on Color Balance |
|---|---|---|---|
| Screen Tension | 30 - 35 N/cm | ± 1.0 N/cm across 4 frames | Uneven tension causes dot distortion and local misregistration of the rosette pattern. |
| Squeegee Durometer | 75 / 90 / 75 Shore A (Triple durometer) | ± 2 Shore A | Soft squeegees (<70 ShA) drive dot gain beyond 30% in critical midtones. |
| Squeegee Angle & Pressure | 75° angle / Minimum shear pressure | ± 2° | Excessive pressure forces ink into yarn core, choking shadow detail. |
| Emulsion Over Mesh (EOM) | 10% - 15% of mesh thickness | ± 2 microns | High EOM forms steep gasket walls, preventing clean release of high-frequency halftone dots. |
| Print Sequence | Y → M → C → K (or C → M → Y → K) | Fixed | Sequence modifies wet-on-wet trapping efficiency and secondary color chromaticity. |
| Observed Defect | Root Photomechanical Cause | Immediate Corrective Action |
|---|---|---|
| Visible Moiré Pattern | Incorrect screen angles or halftone frequency interfering with woven mesh count. | Apply rule: $Mesh \ge 4.5 \times LPI$. Rotate artwork separation 7.5° if interference persists. |
| Color Shift (Red/Blue Cast) | Viscosity or optical density imbalance among primary process ink channels. | Measure with reflection densitometer and equalize ink viscosity (4000-6000 mPa·s). |
| Plugged Shadows (>75%) | Uncompensated mechanical dot gain in RIP curves or excessive squeegee pressure. | Apply linear tone curve correction in RIP (reduce input values by 12-18% in midtones). |
| Washed-out Highlights (<5%) | Under-exposure or harsh washout spray during stencil developing. | Run 21-step Stouffer wedge exposure test to guarantee complete highlight anchor. |
Process CMYK printing on screens shows no mercy to careless press setup. Nine times out of ten, when a job shifts to mud or turns excessively dark after fifty prints, the error isn't in the digital file—it's frame tension variance. If three screens sit at 32 N/cm while one sags at 22 N/cm, that loose screen will dump extra ink and shift registration by half a millimeter. Result? The rosette structure collapses and your color balance is ruined.
Another critical detail: use true transparent, highly pigmented process inks made for CMYK, never thinned-down standard opaque inks. Yellow must allow light to pass through to let magenta and cyan beneath do their optical job. If your inks are semi-opaque, you aren't printing process—you are just mixing paint on cotton.