I am reminded of a quote from a friend of mine who said, "Whatever and whenever you create an art piece always use the best quality materials you can afford and you can be reasonably assured that it won't come back and bite you on the bum in ten years time".
Having quoted Bob, my experience is that most student paints contain lots of fillers to extend the pigment and in some instances even have inferior grade mediums to carry the pigment.
It stands to reason that if a product is not marketed as Artist Quality, then it is not serious artist's quality. Manufacturers would love to be able to claim that their product is as good as that sold as Artist Quality. If it is marked as being good for Student or Beginners then those are the people who may choose to use it. Certainly not serious artists. Surely someone who considers themselves to be a serious artist is better than that.
A thin underpainting is usually a form of primer, a lean mixture (much more Gum Turps than Pigment), mix that is used to block in the painting. "Fat over Lean" means that the outer surface of the painting dries slower than that closer to the canvas. If the reverse is used Oil rich paint closest to the canvas, it will still be drying and moving while the turps rich paint on the outer surface is dry. Consequently the outer surface will crack as the underpaint moves as it dries. Oil paint dries by oxidization not evaporation, and to dry thoroughly can take up to eight months..
An underpainting such as you have described should be dry enough within a couple of days.
I am not sure I have answered your question, perhaps someone else can have a go?
AMS - The Art Specialists.
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