I am trying to set up a proper studio and paints a la Carder method so I have been mixing SDM with cad yellow, burnt umber, alizarin crimson and now ultramarine blue and I discovered my darker colored paints, even when freshly opened from the tube, have this crusty dark separation. The crimson was really bad but I discovered a hole in the tube which must have caused it to leak. In fact all of the tubes ultimately had tears by the folds as I emptied the tubes.
This is the cap in a brand new ultramarine. And this is a reputable paint manufacturer. Is this common?
Suffice it to say, I am emptying tubes and mixing with SDM so the paint will last.