Plastisol ink is known for producing bold, durable prints, but many screen printers notice the same confusing issue: the ink often looks lighter, darker, or slightly different after full curing.
This color shift isn’t a mistake in mixing or printing; it’s rooted in the chemistry of plastisol itself. Understanding how heat affects pigments and PVC resins explains why your print doesn’t match what you saw on the palette.
Why Does Plastisol Ink Change Color When Cured?Plastisol ink changes color because heat during curing alters the transparency of the PVC resin, the way pigments reflect light, and the density of the ink film. As the ink reaches 320°F and the resin fully fuses, pigments become more visible or less visible depending on their type, causing colors to darken, brighten, or shift tone.
In this article, we breakdown the science behind plastisol color shift, including how pigment load, ink viscosity, curing temperature, and ink film thickness influence final appearance. By understanding the chemistry and mechanics, you can better predict color outcomes, prevent unwanted shifts, and achieve consistent results across multiple print runs.
Key Takeaways
Color shift happens because heat changes resin transparency.
As plastisol reaches curing temperature, PVC resins melt and become more transparent, revealing more of the underlying pigment. This often makes darker colors appear richer and lighter colors appear deeper or more saturated.
Pigments behave differently at high temperatures.
Some pigments brighten when heated, while others darken. Organic pigments tend to shift more aggressively, while inorganic pigments stay more stable during curing.
Ink deposit thickness affects final color.
A thicker ink layer traps more light and increases perceived saturation, often making prints look darker after curing. Thin deposits may appear lighter because more substrate shows through.
Under-curing and over-curing produce different shifts.
Under-curing can leave ink chalky or lighter than expected. Over-curing can scorch pigments, deepen color, or shift hues entirely, especially with reds, blues, and low-opacity mixes.
Consistency requires controlling heat and ink variables.
Predictable color results come from stable curing temperatures, accurate dwell times, consistent squeegee pressure, and using inks with reliable pigment loads.