Waterborne screen varnish additives must be selected around mesh transfer, stencil release, drying and the finished print. First stabilize viscosity, screen, squeegee, deposit and dryer. Then separate flow from slip or anti-blocking. One product cited in many generic shortlists—D912R—is explicitly solvent-based and should not enter a waterborne trial.
Mesh, squeegee, rheology and deposit.
Flow, air, pinholes and drying.
Adhesion, gloss, slip, block and wear.
Lock the printing process first
Record substrate and treatment, mesh count and thread diameter, stencil thickness, squeegee hardness/angle/pressure/speed, snap-off, flood cycle, varnish temperature, viscosity at a defined shear, solids, pH, wet deposit, flash, dryer temperature and line speed. Compare candidates with the same screen history and controlled water loss.
Identify where the defect appears: in the screen, immediately after print, during drying, after stacking or during use. Screen drying and mesh marks are not the same as poor leveling; bubbles introduced by mixing are not the same as craters from contamination.
Correct the shortlist
| Termék | Published system fit | Documented range/process | Decision |
|---|---|---|---|
| 3345 | Water, solvent and UV | 100% active; 0.1–1.0% | Eligible flow/leveling screen |
| 3482/3482X | Water only | 80±2% solids; 0.05–1%; staged water dilution | Eligible slip/wear screen with warnings |
| D912R | Solvent-based systems only | 2% active; 0.1–0.25%; grind-stage addition | Exclude from waterborne formulation |
Use 3345 for a verified flow defect
3345 is a polyether-modified polysiloxane published at 100% active and 0.1–1.0% of total formulation. It can be added in grinding, stirring or after production. Screen low, middle and high points against a process-controlled blank. Measure mesh release, print-edge definition, surface waviness, crater count, gloss and recoat or overprint acceptance.
Do not use it to compensate for the wrong viscosity, an overloaded screen, poor substrate treatment or insufficient flash. If a co-solvent such as dipropylene glycol methyl ether is introduced, include it in drying, odor, VOC and block evaluation.
Use 3482/3482X for slip or wear
3482/3482X is an ultra-high-molecular-weight polysiloxane pre-emulsion for water-based coatings and inks. The page reports 80±2% solids and recommends 0.05–1.0%. It must first be diluted with a small amount of water in multiple stages while stirring, then added to the system. The diluted material should not be stored for long periods.
Protect it from freezing and do not mix it with alcohol solvents. The page warns of pinhole risk. Treat 3482X’s thickener and better dilution stability as a rheology change to be measured, not a free benefit. Release only if slip or abrasion improves without pinholes, haze, gloss shift, poor adhesion or screen instability.
Exclude D912R from waterborne trials
D912R is a 2% active fluorocarbon-modified polysiloxane solution in isobutyl adipate. Its product page specifies solvent-based application areas and a 0.1–0.25% range, with grind-stage addition. That evidence does not support use in a waterborne screen varnish. Do not test it merely because the page also mentions coatings and inks generally.
If foam is the actual waterborne problem, locate its entry point and request a current waterborne-compatible defoamer shortlist with active content, carrier, dosage and addition instructions. Qualify compatibility and print behavior before production.
Build two separate experiments
| Experiment | Variants | Primary response | Release gate |
|---|---|---|---|
| Flow | Control plus 3345 low/mid/high | Transfer, leveling, craters | Dry, adhesion, gloss, block |
| Slip/wear | Control plus 3482/3482X low/mid/high | COF or agreed slip panel, abrasion | Pinholes, haze, adhesion, printability |
| Foam | Process study before product | Wet density, foam decay, microbubbles | Only waterborne-compatible candidates |
Measure adhesion after full drying
ASTM D3359 was developed for relatively ductile coatings on metal. If the screen varnish is on another substrate, agree whether the method is suitable and report the limitation. Keep film thickness, conditioning, cut spacing, tape and removal technique fixed, and note the actual failure plane.
Measure gloss and abrasion comparatively
ASTM D523 measures specular gloss. Use the same geometry and substrate background. ASTM D4060 provides a Taber abrasion comparison for organic coatings. State wheel, load, cycles, conditioning and endpoint; do not convert one laboratory wear result into a universal service-life claim.
Test blocking and finishing
Stack printed specimens under defined pressure, temperature, time and face-to-face or face-to-back orientation. Record offset, sticking, gloss transfer and surface marking after a fixed recovery time. Then test die cutting, folding, overprinting, laminating or bonding if those operations follow. Surface slip can reduce friction yet harm an adhesive or overprint.
Repeat the best candidate after one controlled press restart and after a defined varnish hold time. This exposes viscosity drift, screen drying and dilution instability that a single fresh laboratory print can miss.
Decision rules
- Fix mesh transfer and drying before modifying the surface.
- Use 3345 for flow; use 3482/3482X for a defined slip or wear target.
- Exclude solvent-only D912R from the waterborne shortlist.
- Reject gains that introduce pinholes, haze, poor adhesion or finishing failure.
Information to send
Provide substrate and treatment, varnish resin, solids, pH, viscosity curve, mesh, stencil, squeegee, deposit, dryer, first defect and required gloss, coefficient of friction, block, abrasion, adhesion and finishing limits.
Ask Longchang for a waterborne screen-varnish study that matches your press.