Tonwertsteigerung

Tonwertsteigerung is a phenomenon observed in offset printing where printed dots appear larger on the paper than they did on the printing plate. This results in darker tones and a loss of fine detail, particularly in mid-tones and highlights. The effect is caused by several factors, including the spreading of ink into the paper fibers and the pressure applied during the printing process.

The degree of Tonwertsteigerung can vary depending on the paper type, ink properties, printing speed, and the specific press conditions. Coated papers generally exhibit less Tonwertsteigerung than uncoated papers because the ink sits on the surface rather than being absorbed. Finer dot patterns are more susceptible to this effect.

Printers and pre-press professionals employ various techniques to compensate for Tonwertsteigerung. In pre-press, this involves applying a "UCR" (Under Color Removal) or "GCR" (Gray Component Replacement) strategy, which reduces the amount of CMY inks in neutral and dark areas and replaces them with black ink. This not only helps control Tonwertsteigerung but also saves ink and improves gray balance. During the printing process, adjustments to ink density, pressure, and roller settings can also mitigate the effect.

Understanding and controlling Tonwertsteigerung is crucial for achieving accurate color reproduction and maintaining image quality in offset printing. It is a fundamental consideration in the pre-press workflow and on the printing press to ensure that the final printed product matches the intended design.