Recyclable Coatings
Water-based varnish is a strong route to plastic-free paper finishing — but "water-based" is not the same as "recyclable." Here is how to substantiate the claim.
A water-based overprint varnish uses water as the volatile carrier instead of solvent, which lowers VOC burden and avoids solvent drying infrastructure. But recyclability and "plastic-free" status are properties of the whole package — coating, inks, adhesives and the destination recycling stream. A water-based film former is still a polymer; its effect on repulpability must be measured, not assumed.
| Parameter | Typical range | Common test method |
|---|---|---|
| Non-volatile content | 20–50 % | ASTM D2369; ISO 3251 |
| Viscosity | 50–2,000 mPa·s | ASTM D2196; ISO 2555 |
| pH | 7.0–9.0 | ISO 976; ASTM E70 |
| Dry coating weight | 0.5–4.0 g/m² | Internal |
| 60° gloss | 30–90 GU | ASTM D523; ISO 2813 |
| Coefficient of friction | 0.15–0.50 | ASTM D1894; ISO 8295 |
| Rub resistance | 50–500 cycles to end-point | ASTM D5264; Internal |
| Blocking resistance | None / slight (defined conditions) | ASTM D4946; Internal |
| VOC content | 0–50 g/L (formula- and jurisdiction-dependent) | ASTM D3960; ISO 11890-2 |
Repulpability is assessed by pulping the coated paper and measuring fiber recovery and screening (CEPI and PTS-RH methods are common references), then checking acceptability against the target mill or protocol. Results are structure- and facility-specific. The right evidence chain is: lab repulpability test → target recycling stream confirmation → claim limited to what the data supports.
| Defect | Root cause | Corrective |
|---|---|---|
| Poor wetting / craters | Low surface energy, contamination, ink incompatibility | Clean pretreatment; adjust surface tension |
| Bubbles / pinholes | Over-mixing, trapped air, wrong defoamer | Reduce entrainment; de-aerate; adjust defoamer |
| Blocking / roll sticking | Incomplete dry; residual tack; hot rewind | More effective drying; cooler web; tension control |
| Paper curl / wave | Single-side moisture; uneven drying | Balance coat/dry; control web moisture; lower thermal gradient |
| Weak fold / crack | Coating brittleness; overcoat; low flexibility | Adjust binder flexibility; coat weight; drying |
No. 'Water-based' describes the carrier, not the end-of-life performance. Recyclability depends on the whole package structure — coating, inks, adhesives and the target recycling stream. The claim must be supported by testing against the actual recycling path.
Repulpability is assessed by pulping the coated paper and measuring fiber recovery and screening (e.g., CEPI and PTS-RH methods), then checking acceptability against the target mill or protocol. Test the finished construction, not the varnish alone.
Not necessarily. VOC content depends on the formulation and the applicable jurisdiction's definition and method. Claim 'low VOC' with a test report and method cited rather than 'zero VOC' by assumption.
These are independent, measurable trade-offs. Set targets per application, screen at multiple coat weights, and verify each property on the finished sheet.
Tell us your substrate, print process, target gloss/rub and destination market. We'll propose a water-based varnish and the test plan to substantiate your recyclability claim.
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