Overprint Varnish
10 L 4160
Application
Overprint varnish 10 L 4160 is a particularly good-drying and abrasion-resistant type of print
varnish, imparting neither a gloss enhancement nor a matting effect to the printed surface but
keeping its appearance more or less unchanged.
It is advantageous to use this varnish especially
• for jobs showing a lack of drying or rub resistance,
• as a protective coating for prints on matt-coated stocks to prevent scuffing or carbonizing effects.
This varnish can be run with or without damping solution, whereby the latter is to be preferred
if prints have insufficiently dried. Overprint varnish 10 L 4160 lends itself ideally for wet-on-dry
application but can also be printed wet-on-wet.
Special properties
• Silky surface gloss.
• Quick oxidative drying.
• Fast setting.
• Very good pile behavior.
• Very good abrasion resistance.
• Little tendency to yellowing.
Advantage of print varnishes over other coating systems
In the field of package printing, print varnishes have now largely been replaced by alternative
coating systems, for example by dispersion coatings. In other areas, however, the use of print
varnishes is essential.
Some of the reasons for this:
• They guarantee spot varnishing true to register.
• It is possible to coat light-weight papers with the substrate remaining dimensionally stable.
• Oil-based varnishes can be seen as unpigmented offset printing inks. They are therefore
handled in the same way, which includes the use of the same washing mediums. There is no requirement for the inks to possess particular
fastness properties (for example resistance to solvents or alkalis).
Special remarks
Note should be taken of the following when using print varnishes:
In contrast with dispersion coatings and UV coatings, print varnishes are comparatively slow-drying.
The mechanism of oxidative drying, which produces stable coating films in print
varnishes as a result of the cross-linking of fatty acid chains, can occupy several hours or even
days, depending on the drying conditions. Drying can be accelerated by the use of IR
radiators. However, pile temperatures of more than 35 °C must always be avoided as there is a risk
of blocking. The use of inks in pre-printing that stay fresh can result in the delaying of varnish
drying, especially on papers with low absorption capacity.
Contact yellowing cannot be completely ruled out when print varnishes are used. The cause
of this is that volatile, yellowish colored fission products are formed during oxidative drying;
these products can be deposited in the paper coating or even react chemically with
constituents of the coating.
Standard print varnishes are not suitable for finishing food packaging. The fission products
necessarily formed as part of the oxidative drying process can affect the smell and taste of
the contents which prohibits their use.
Printing additives
The specified print varnish is ready for printing and can normally be used without the help of
additives. If in exceptional cases it is necessary to reduce the tack for papers that are
particularly susceptible to picking, Linseed oil / Printing oil 1405 should be used.
It is not advisable to add drying agents to print varnishes as over dosage tends more to inhibit
drying rather than promote it. The extraction of drying agent at higher levels of dampening
solution feed can be counteracted by the use of Fountain drier HYDROSIC 8041 09.
