Q: I want to use chalk pastels on unprimed canvas and have the colors achieve a melted look. How might I do this?
A: Pastels are water soluble, so you can achieve this effect
by mixing dust from the pastel sticks with water. However, when the
paint dries the canvas will pucker. A better choice would be to use
acrylic matte medium, thinning the medium with water if necessary.
Please remember that any pigments will likely darken and perhaps lose
some brilliance when mixed with water.