How Screen Printing Inks Cure And Why It Matters
By The Velocity Wear Team
Screen printing ink does not dry, it cures. Plastisol is a suspension of PVC particles in a plasticiser, and it only becomes a solid, flexible film once the whole ink layer reaches roughly 160 degrees Celsius. Water-based ink has to lose its water first and then, in most formulations, cross-link. Get either process wrong and the print looks flawless on day one and cracks, fades or lifts within a handful of washes.
Drying And Curing Are Not The Same Thing
Drying just means the liquid carrier has left. Curing means a change has happened that cannot be undone. Plastisol will sit wet in a screen all week and never dry, because there is nothing in it to evaporate. Apply enough heat and the PVC particles absorb the plasticiser, swell and fuse into a single continuous film locked around the fibres. Water-based ink genuinely does dry, which is why it skins over in the mesh the moment a printer stops for five minutes, but drying on its own does not make it durable. The binder still has to set.
Gel Stage Versus Full Cure
On a multi-colour job you will see the press flash the print between colours. That flash only gels the ink: it firms the surface enough that the next screen can pass over it without smearing. It is not a cure, and a printer who treats it as one will produce a garment that fails. The finished film has to reach temperature all the way through, not just at the top surface. A print that has cured on top but stayed soft underneath will pass a casual fingernail test and still crack the first time the wearer stretches it.
Water-Based And Discharge Inks Ask For More
With water-based ink, dwell time matters at least as much as peak temperature, because the water has to be driven out of the fabric before the binder can set. A humid workshop genuinely changes the outcome. Discharge prints add another layer of complexity: the activator needs both heat and time to break down the garment dye, and the reaction carries on for a short while after the garment leaves the dryer. That is why a discharge print sometimes looks paler coming off the press than it does the next morning.
It Is The Ink Temperature That Matters, Not The Oven
The dryer display shows the chamber temperature. What actually matters is the temperature of the ink film itself, and those two numbers can be a long way apart. A thin single-colour print on a light tee gets there quickly. A thick white underbase on a 400 GSM hoodie sits on a mass of fabric that soaks up heat, so the same belt speed can leave the ink short of cure while the display insists everything is fine. Dark garments absorb radiant heat faster than white ones too, so a mixed-colour order can behave differently across the same run. Careful printers verify with a probe or temperature strips rather than trusting the dial.
How Undercure Shows Up On Your Order
- The print cracks along fold lines, usually at the shoulders and the hem first.
- Colour transfers onto the inside of the garment or onto other clothes in the wash.
- The surface goes tacky in a warm delivery van and garments stick to each other in the box.
- Fine detail wears away while thick areas survive, giving a patchy, half-erased look.
- Everything seems fine for two or three washes, then the print fails all at once.
Overcuring Is A Real Problem Too
Cure is a window, not a target you can overshoot safely. Too much heat scorches synthetic fibres, yellows white ink, and shrinks the fabric around the print so the panel puckers. On polyester it also invites dye migration, because the garment dye turns to gas at those temperatures and moves up into the ink. Running the dryer hotter is not a safety margin. It just swaps one failure mode for another.
“"A print you can pick off with a thumbnail in the warehouse was never going to survive a tumble dryer."”
What To Ask For As A Buyer
You cannot inspect cure by eye, so ask how it is being verified and ask for a sample you can wash. Put it through a normal cycle three or four times at the temperature your staff or customers will actually use, then stretch the print across your knuckles. Cured ink stretches and returns. Undercured ink crazes. It is worth requesting this early, because production runs from artwork approval rather than from the day you place the order, and a wash test done at the start costs you nothing in lead time.