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This shouldn't happen. It is

This shouldn't happen. It is caused by faulty manufacturing.
Either by wrong ratio of the ingredients of the binding or wrong mixing/processing with the pigment. Or both!
In any case the colour that separates from the binder in the tube, sooner or a little bit later will separate from its binder on the paper. In order to get how this thing works think that the binder is some sort of glue for the pigment.