For years, screenprinting has been a popular printing method for making large numbers of (advertizing) posters. Its main attraction is that it is easy and relatively cheap. But beyond that it also plays a significant role in artworks and handicrafts - where the water-based version is particularly prominent, not least because the person at work is not thereby exposed to hazardous solvents. In schools the water-based method is the only one possible for just this reason.
Water-based screenprinting paints are available in ready-to-use paint admixtures or as a combination of pigments and a binder or as ready-to-use paint with a binder. The Lascaux screenprinting paste is among the last-named group, a water-based binder that can not only be mixed with all acrylic paints but with gouache and tinting paints as well. This addition will not meaningfully affect the important attributes of the respective paints (transparency can, however, increase a bit). This means that once a high quality, vibrantly coloured, pigment rich acrylic paint has been mixed with the paste, a correspondingly more vibrant print will result than would have resulted from a paint with less pigments.
Processing: First mix the colours to obtain the desired hue, after which the paste should be added. Lascaux recommends that the ratio of paint to paste should be 1:1. Our experience shows that using less paste is better, especially in the cases of gouache and tinting colours. As the amount of paste increases so does the length of the working, or alternatively, drying time. In addition, the paste thickens the paint whereby it will tend not to run as much. Too little paste can lead to the paint (too quickly!) drying on the screen while too much paste can leave the mixture "underbound" (incomplete curing). The right mixture for the various individual needs and the specific working conditions is, as is always the case, best determined by trial and error. Standard painting auxiliaries (retardents, transparent varnish, etc.) can also be used in the customary ways.