Best to stick to paints made by marblers for the marbling process for those
reasons, or at least ones that have been heavily tested by marblers. So
many of the pigments are not compatible with the marbling process or even
if they are, may not be friendly to other pigments that also are. Sometimes
certain chemical and physical properties make them sink more quickly,
spread too much, etc. Unfortunately it isn't always a matter of picking a
pretty color in marbling. A lot of great colors just plain old do not work!
I find that a quick dunking in weak alum water (1tbs. per 2-3 cups hot
water) is sufficient for fabrics, if it is aluminum sulphate or aluminum
potassium sulphate....the best kind for marbling. I find that I always need
alum with fabrics, but can use my acrylics on paper (almost all papers)
without alum. Not sure if this is true of other acrylics. The color is just
as intense as if alum was used.