# Solid density

The solid density is a measured variable in the print and is determined with the help of a densitometer . It is the optical density of a surface that is continuously covered with color (full-tone surface, as opposed to a grid surface). ${\ displaystyle D_ {V}}$

Fertility diagram of a set of process colors on a paper

Since the thickness of the ink layer cannot be measured on the printing press, the optical density of full-tone fields is used as an aid for color control. The quasi-linear areas can be used from the yield diagrams for printing inks to assign an application of color to a density measurement. In printing practice, machines are controlled manually or automatically. This applies to the offset and high pressure , as far as zone regulations exist. The gravure , screen printing and the zone-free offset and letterpress (mostly flexographic ) machines have to regulate the transfer of ink by modifying the printing form or the inking device (here: anilox roller ).

The full tone density of a color depends not only on the thickness of the color layer, but also on the pigmentation of the color (yield), the surface of the printing material ( roughness , absorbency, inherent coloring) and the fine distribution of the color layer thickness (pearlescence).

ISO 12647-2, which is integrated in the process standard offset printing in Germany, prescribes colorimetric measurement values for standard-compliant scale printing . Print shops without a spectrophotometer (or densitometer ?), On the other hand, often use empirically determined specifications for the solid density.

The increasing use of computers in printing machines and new, compact spectrophotometers make it easier to control the ink zones via colorimetric measurements. In this respect, the importance of full tone density is decreasing. However, it is still indispensable when measuring tone values ​​and tone value increases, as well as when determining the relative print contrast .

## Individual evidence

1. Helmut Kipphan (Ed.): Handbuch der Printmedien. 1st edition. Springer, Heidelberg 2000, ISBN 3-540-66941-8 , p. 104
2. Rudi Riedl, Dieter Neumann, Jürgen Teubner: "Technologie des Offsetdrucks", 1st edition, VEB Fachbuchverlag Leipzig 1989, ISBN 3343005274 , p. 321
3. ^ H. Teschner: Druck- und Medientechnik, 13th edition. Christiani, Konstanz 2010, ISBN 978-3-86522-629-7 , p. 604
4. Helmut Kipphan (Ed.): Handbuch der Printmedien. 1st edition. Springer, Heidelberg 2000, ISBN 3-540-66941-8 , p. 134
5. Helmut Kipphan (Ed.): Handbuch der Printmedien. 1st edition. Springer, Heidelberg 2000, ISBN 3-540-66941-8 , p. 132
6. Effect of the color layer thickness distribution on the color in multi-color screen printing , FOGRA research report 50.031 Author Pertler, H .; Rosenberg, A. 2002