GRAVURE · SOLVENT · FINE FINENESS
Gravure inks are solvent-based and run at high line speeds, which puts the emphasis on fine, stable dispersion and on temperature control during milling. Coarse particles or a drifting distribution show up immediately as doctor-blade lines and poor print density.
Gravure ink quality is decided in the mill: fine, narrow particle distribution plus tight temperature control. Solvent handling also requires explosion-proof electricals and, where used, solvent recovery.
Resin is dissolved in solvent to make varnish, pigment is wet out under high shear, and the millbase is milled to the target fineness. Letdown adjusts viscosity and solvent balance; filtration and filling follow.
Solvent-based systems are closed where possible to limit evaporation and operator exposure, and the electrical installation is specified for the hazardous area.
Solvent loss and temperature rise both change viscosity, and viscosity change alters the milling behaviour. A mill that runs hot will show a drifting fineness across the batch even if all other settings are fixed.
Jacketed chambers with chilled water and outlet temperature monitoring are the practical answer; reducing feed rate is the second lever.
Doctor blade lines, poor transfer and inconsistent density usually trace back to oversize particles or a wide distribution. Both are milling and filtration problems, and neither is fixed by adding solvent.
| Stage | Equipment | What it decides |
|---|---|---|
| Varnish | Stirred tank with temperature control | Resin dissolution consistency |
| Dispersion | High-speed disperser | Pigment wet-out |
| Milling | Disc-type or pin-type horizontal bead mill | Fineness and distribution |
| Filtration | Bag filter | Oversize removal |
| Filling | Filling machine | Pack accuracy and solvent loss |
Gravure inks are milled to a fine micron-range distribution, finer than typical flexo inks, because the engraved cells are small. The exact target depends on the cylinder engraving and should be confirmed with the ink formulation.
By closing transfer points, limiting open surface area, controlling temperature and filling promptly. Solvent balance is part of the specification, not an afterthought.
Solvent-based production requires motors and controls rated for the hazardous area. The classification is set by the solvent and the installation, not by the machine alone.
Often yes, with cleaning between products. The difference is mainly the fineness target and the solvent system.
Send the ink type, the pigment system, the target fineness, the batch size and whether the line must run solvent or water-based products. POLYC MACHINE engineers will confirm the configuration and state where a trial is required before performance is guaranteed.