Water-based matrix penetrates deep into the core of yarn fibers.
Reducing agent breaks the chromophore bonds of the reactive dye.
Discharged and re-pigmented fiber with absolute soft hand-feel.
| Component / Parameter | Target Dosage | Tolerance | Technical Function & Notes |
|---|---|---|---|
| Water-Based Discharge Base | 90% - 94% (by weight) | ± 1.0% | High-penetration acrylic resin with low-viscosity binders. |
| Activator Agent (ZFS / ZCS) | 5% - 6% (Powder / Liquid) | Strict ± 0.5% | Zinc/Sodium Formaldehyde Sulfoxylate. Below 4%, discharge reaction remains incomplete. |
| Discharge-Safe Pigments | 1% - 5% (depending on shade) | ± 0.2% | Use exclusively pigments tested for discharge stability (reduction resistant). |
| Ink Bath pH Level | 8.5 - 9.5 pH | ± 0.3 pH | Maintain with ammonia/stabilizers. Acidic pH (<7.0) triggers premature decomposition. |
| Pot-Life (Mixed Batch) | 4 - 8 Hours (at 21°C) | Max 12h | Progressive decay of active reducing agent. Mix fresh batches for dark garments. |
| Process Stage | Optimal Set-Point | Impact on Final Print Quality |
|---|---|---|
| Mesh Selection | 43 threads/cm (110 tpi) for White 62-90 threads/cm for Colors |
High mesh counts (>100 tpi) restrict wet ink deposit, preventing complete fiber penetration. |
| Squeegee Profile & Durometer | 65 Shore A (Square Edge or Triple 65/90/65) | Sharp edge set at 75° angle forces liquid ink mass deep into yarn structure. |
| Off-Contact Distance | 2.0 mm - 3.0 mm (High Tension: 22 N/cm) | Clean snap-off prevents fluid ink drag and maintains razor-sharp edge definition. |
| Curing Tunnel Settings | 165°C - 170°C actual garment temp Dwell time: 150 - 180 seconds |
CRITICAL: Requires forced exhaust ventilation (min 1500 m³/h). Without steam removal, reaction stalls. |
| Observed Defect | Root Chemical / Physical Cause | Immediate Corrective Action |
|---|---|---|
| Yellowish / Brownish Cast | Garment dyed with non-reactive dyes (e.g., Direct dyes or untreated poly-blends). | Perform spot-discharge drop testing on sample fabric before launching production. |
| Chalky / Flaking Print Surface | Over-curing temperature or lack of moisture in fiber during reduction stage. | Reduce tunnel temperature to 160°C and extend dwell time to 3 full minutes. |
| Heavy / Stiff Hand-Feel | Excessive binder deposit or using hybrid water/plastisol base formulations. | Increase mesh count (move from 43T to 62T) and decrease squeegee pressure. |
| Color Loss at End of Shift | Active ZFS activator expired inside the screen ink well. | Dump remaining ink well volume and replenish with freshly mixed activated ink. |
I constantly see screen printers panicking because a discharge print on a black shirt turns out dull grey or muddy brown. The cause is almost always identical: they bought cheap shirts dyed with direct dyes instead of reactive dyes, or labeled as 100% cotton while containing an inner 20% polyester core that discharge chemistry will never touch.
Another golden rule: inside the dryer, heat isn't the only factor—air extraction is everything. If your tunnel exhaust fails to sweep away the evaporated formaldehyde gas and moisture, the shirt gets hot, but the reduction process freezes. Keep your filters clean and demand technical data sheets (TDS) for every garment lot before committing to a 1000-piece run.