UV screen varnish additives should be selected after the defect is named. A thick screen-applied varnish can fail through poor leveling, trapped air, incomplete UV conversion, weak adhesion, excessive slip, rub loss or blocking. One silicone additive is not a cure for all seven.
The most defensible first routes are CHLUMIAG® 3500 for a documented acrylic-functional radiation-cure leveling route, CHLUMILE® 3432 for general cross-system leveling, and CHLUMIAF® 3062 only when foam or entrained air has been measured. The public 2750 family page does not support the previous reactive or reverse-varnish assignment.
UV screen varnish decision map
| Observed failure | First evidence check | Route to screen |
|---|---|---|
| Orange peel, poor flow or uneven gloss without bubbles | Hold mesh, wet film, rheology and UV dose constant | 3500 or 3432 |
| Wet bubbles become cured pinholes | Track air after mixing, flood stroke, print stroke and dwell | 3062 |
| Tacky surface, weak solvent resistance or blocking | Measure lamp output, line speed, film build and through-cure | Fix cure before additive escalation |
| Adhesion or overprint fails after surface improvement | Locate substrate/coating or intercoat failure | Reduce surface modification and retest |
| Produk | Published fit | Supplier guidance | Boundary |
|---|---|---|---|
| CHLUMIAG® 3500 | Acrylic-functional radiation-cure leveling; UV, solvent and water-based systems | 0.05–1%; any stage or later; alkane/aromatic dilution | Protect from light/heat; avoid additive mixtures; confirm UV conversion |
| CHLUMILE® 3432 | Polyether-modified polysiloxane leveling route; UV, solvent and water-based | 0.05–1%; any stage; water/alcohol/alkane/aromatic dilution | Not documented as a reactive network-building route; avoid mixing |
| CHLUMIAF® 3062 | 100% active nonionic silicone defoamer; UV, solvent and water-based | Printing inks 0.1–0.5% total formulation | Use only for measured air; solvent dilution needs stability and defoaming tests |
Use 3500 for the documented reactive UV route
The 3500 product page states that it contains reactive acrylic functional groups and can crosslink into the polymer network in radiation-curing systems. That supports a reactive UV screen, but not an assumption of complete conversion in every oligomer, monomer, photoinitiator, pigment or lamp combination.
Run a low-to-high 0.05–1% ladder while holding UV dose, peak irradiance, spectrum, line speed and wet film constant. Record surface and through-cure, gloss, leveling, slip, adhesion, rub, blocking and recoat. A smoother surface is not proof of cure.
Use 3432 for general leveling evidence
3432 is a cross-system leveling and wetting route with the same published 0.05–1% range. It can be useful when the decision is surface balance rather than reactive incorporation. Compare it alone against the blank and 3500; the public page advises avoiding mixtures with other additives.
Check crater suppression, print definition, edge hold, gloss uniformity, slip, adhesion and subsequent decoration. Excess surface activity can improve appearance yet weaken intercoat acceptance or alter blocking.
Use 3062 only when air is demonstrated
3062 is a defoamer, not a general cure or leveling additive. Standardize mixing, ink return, screen flood, squeegee speed, dwell and substrate temperature. Compare wet-film bubbles with cured pinholes so dewetting is not mistaken for foam.
If solvent dilution is used, follow the product-page instruction to test storage stability and defoaming performance first. Select the lowest level that controls air without causing craters, haze, gloss loss, adhesion loss or poor recoat.
Why 2750 leaves the first shortlist
The current shared 2750/2760/2780/2505 page describes multi-component modified polydimethylsiloxane, UV/solvent compatibility, 0.1–3% and variant viscosities. It does not document acrylic reactive groups, network crosslinking, or a 2750-specific reverse-varnish function. Those claims require a current individual TDS and supplier confirmation.
Build a controlled screen-varnish trial
- Fix the print process. Hold mesh, emulsion, squeegee, stroke, wet film and dwell.
- Fix the UV process. Record lamp type, age, spectrum, dose, irradiance, line speed and cooling.
- Use one additive at a time. Run blank plus a compact ladder.
- Condition before judging. Use the same post-cure time, temperature and humidity.
- Challenge downstream work. Include rub, stack/block, adhesion, foil, overprint or die-cut needs.
Measure cure and print performance separately
ASTM D5402 uses solvent rubs to assess solvent resistance of chemically changing coatings, but explicitly warns that solvent resistance alone does not prove full cure. ASTM D5264 compares abrasion resistance of printed materials under controlled laboratory conditions. ASTM D3359 is a limited tape-adhesion rating method and must be matched to substrate and film thickness.
Report UV measurements, wet/dry film, tack, solvent rub, gloss, haze, rub loss, adhesion failure mode, COF, stack temperature/pressure, odor and downstream converting. Use production substrate and ink beneath the varnish.
Common selection errors
Calling every pinhole a foam defect
Track the defect from wet mixing through cure. Air, dewetting, substrate outgassing and incomplete cure require different corrections.
Calling 2750 reactive without product-specific evidence
The public family page does not substantiate the former reactive or reverse-varnish positioning for 2750.
Approving gloss before cure
Appearance can pass while through-cure, rub, adhesion or blocking fails. Keep those gates separate.
Request a UV screen-varnish shortlist
Send the varnish oligomer/monomer, photoinitiator, pigment or matting, current additives, substrate and underlying ink, mesh, film build, UV equipment, line speed, defect photos, and cure, adhesion, rub, slip, blocking and converting limits. Ask Longchang Chemical to compare 3500, 3432 or 3062.