glycerine rivers

When I make soaps with colors that are quite different, for the last few batches, anyway, I have started to get what appears to be a glycerine line between the colors. At first, I figured maybe it was a temperature difference thing, but the layers are usually within 5 degrees of each other when...

The other day, I asked about mixing colorants and someone wisely suggested that I start a soap coloring thread. So here it is! I'd love to know what type colorants people use and prefer and how they mix them. I've seen people mixing oxides, pigments, powders and micas using oils, glycerine...