Wax Emulsion & Powder
Wax is the quiet workhorse of surface finishing — but the benefit lives at the surface, and so do the failure modes. Here is how to select and dose it.
During film formation, wax particles migrate to the surface and modify surface energy. The practical outcomes are a lower coefficient of friction (slip), better rub and mar resistance, and — depending on particle size and loading — a matting contribution. The effect is governed by wax chemistry (PE, paraffin, carnauba, modified wax), particle size (D50/D90), hardness, loading and compatibility with the binder and substrate. It is a surface property first, not a bulk property.
| Parameter | Typical range | Common test method |
|---|---|---|
| Particle size D50 (emulsion) | 0.5–10 µm | ISO 13320; ASTM B822 |
| Particle size D90 | 1–20 µm | ISO 13320; ASTM B822 |
| Melting point | 50–160 °C | ASTM D87; D127 |
| Solids content (emulsion) | 20–50 % | ISO 3251; ASTM D2369 |
| Active wax content (powder) | 95–100 % | Internal |
| pH (emulsion) | 7.0–10.0 | ISO 976; ASTM E70 |
| Slip efficiency (COF reduction) | 0.10–0.40 | ASTM D1894; ISO 8295 |
| Matting efficiency (ΔGU) | 5–40 vs. control | ASTM D523; ISO 2813 |
| Abrasion resistance | +20–200 % vs. control | ASTM D4060; D5264 |
For wax emulsions, a typical screening start is 0.5–5 % of total coating solids; for wax powders, 0.5–3 % of total formulation weight. Optimize by dosing trials measuring coefficient of friction, gloss, abrasion and interlayer adhesion. Note that finished coating dry weight for thin paper/film finishing is often 1–5 g/m², so the absolute wax load is small — precision in letdown matters.
| Failure | Root cause | Corrective |
|---|---|---|
| Emulsion break / separation | pH drift, incompatible electrolyte, over-shear, poor storage | Verify compatibility; adjust addition order; respect storage limits |
| Over-slip / poor printability | Wax concentration or migration too high | Reduce load; choose low-migration wax; test ink adhesion |
| Poor interlayer adhesion | Wax bloom/migration forms low-energy surface | Lower load; compatible wax; verify overcoat conditions |
| Uneven gloss / haze | Agglomeration, incompatible refractive index, poor dispersion | Improve dispersion; select particle-size grade |
| Insufficient abrasion resistance | Wrong wax hardness; poor dispersion; low load | Optimize wax chemistry and active load; test |
Wax additives migrate to the surface during film formation to modify surface properties: they reduce the coefficient of friction (slip), improve rub and mar resistance, and can contribute matting. The effect depends on wax chemistry, particle size, hardness, loading and compatibility.
For wax emulsions, a typical screening start is 0.5–5 % of total coating solids; for wax powders, 0.5–3 % of total formulation weight. Optimize by dosing trials measuring coefficient of friction, gloss, abrasion and interlayer adhesion.
Yes if overdosed or poorly chosen. Excessive surface migration lowers ink adhesion and creates a low-energy surface that hurts overprint or lamination. Wax can also affect repulpability depending on type and loading, so verify the finished system.
Emulsion instability comes from pH drift, incompatible electrolytes, shear beyond the formula limit, or poor storage history. Verify pH, viscosity and compatibility with surfactants, binder, pigment and electrolytes, and follow storage limits.
Tell us your base coating, target COF/gloss/rub and substrate. We'll recommend a wax emulsion or powder grade and a dosing starting point, with TDS on request.
Contact an engineer