GENERAL INFORMATION
ABOUT ACRYLAC WATER-BASE VARNISHES
This Technical Information provides data about the viscosity, film forming,
storage, self stability and freezing sensitivity of water-base dispersion varnishes.
Check out the links on the Technical, processing, application, printing,
drying, draining the varnish and the odor effect of the ACRYLAC varnish.
Application-related information
Viscosity
Dispersion varnishes are adjusted to an optimum processing viscosity when shipped. We can
do this, however, only if we have the following information:
• Will the varnish be processed in an indirect or direct application system in a sheet-fed offset press?
• Make and model of the application system.
• Make and model of the coating machine, if applicable.
The variable determined for dispersion varnishes is not viscosity, but draining time using a
4mm DIN cup. Procedures for this determination are defined in DIN 53 211. If application-related
considerations dictate a reduction in viscosity, dilute by slowly stirring in water. Maximum
dilution must not exceed 5%, otherwise important varnish functions may be impaired. On
request, we can provide graphs of draining time as a function of dilution for any of our varnishes.
Film forming
Film forming in the applied varnish is critically influenced by its processing temperature. Our
dispersion varnishes are designed for a minimum film forming temperature ([MFT] DIN 53 787)
of between +5 and +10 °C. For safety reasons, the varnish should be allowed to come to room temperature before being
processed. Working at a temperature below the MFT usually results in wetting and adhesion
problems. These problems can also occur if air at a temperature below 40 °C is blown on prior to stacking
in order to promote drying (e.g. air ductor). The reason in this case is the heat extracted by
evaporation.
Storage and shelf stability
Our dispersion varnishes should be stored at room temperature whenever possible (see above).
Slight increases in viscosity are possible after storage times of several months (on the order
of 20% of as delivered viscosity) caused by formation of structures in the varnish. By stirring
it thoroughly it is generally possible to obtain again the original viscosity. Only in exceptional
cases, however, is viscosity correction by dilution with water required. The characteristics of
the varnish are not impaired by such corrections (max. 2–3% water).
Storage temperatures exceeding 40 °C should be avoided, since they encourage more
pronounced increases in viscosity. Special varnishes have a limited shelf life, e.g. weldable varnishes can be stored for 6 months.
Please note the special instructions in the relevant Technical Information for each product.
Freezing sensitivity
Dispersion varnishes will freeze at temperatures below –5 °C (depending on varnish type); this
can occur during extended transport in winter. It is important that frozen dispersion varnishes
be slowly thawed in the container at room temperature. They must not be processed until they
have come to room temperature after thorough mixing. Storage temperatures should always
be maintained above 0 °C.
