To paint with oil pastels or watercolor on top of life drawings, you have to coat your paper to protect it. You can use either clear gesso or gel medium to do so and still be able to see your drawing underneath.
Here is a comparative study of gel medium and clear gesso over my life drawings, with watercolor, oil pastels and mixed media.
I am working on a series of life drawings that I made in our weekly life drawing class ( You can visit our North Vancouver life drawing class website here). I like to keep the original drawings and then paint over them or use pastels.
You might also be interested in: An alternative to Yupo paper: Gel medium on regular paper.
Making your drawing paper waterproof:
Both clear gesso and gel medium are white but will dry clear.
I used a soft brush to spread the medium on paper. Some of the brushstrokes were visible once dry, and I like this effect.
For the clear gesso, I used a stiffer brush so the brush strokes would be even more visible.
Oil pastels on paper covered in gel medium or clear gesso:
Sometimes, before starting to work with oil pastels, I like to outline my figures with a marker.
If you try doing that, you will notice that you can still see details like the features of the face or fingers under a light layer of light colored pastel. You could add this outline before treating the paper with gesso or gel medium, or after. Before is easier because the gritty surface of clear gesso makes it a bit hard to use the marker, but it is still feasible.
Pastels are thick so details like fingers would be lost otherwise.
Using clear gesso on the paper will give a grittier texture than gel medium. That makes it easier to use with oil pastels, although you could still use oil pastels on top of the medium painted paper.
Medium will dry with a smoother texture but you can still use oil pastels over it, but they somewhat “slide” on the medium.
Gesso has a grittier texture that is more suited to dry pastels and oil pastels. The oil pastels might make some little aggregates on the gesso, but you can brush them away easily.
What I like with oil pastels is how you get interesting rich fields of broken colors when mixing colors.
Most of the outlines will be still visible, even if lightly covered in light colored pastel.
In that example, I applied different colors of pastels but it is difficult to get a blended color with the pastels only.
By applying baby oil with a cloth, you can blend color more easily.
Watercolor on paper covered with gel medium or clear gesso:
Gel medium on paper makes it more water-resistant than clear gesso, so the watercolor paint will dry and react a bit as it would on yupo paper, as paper painted over with gesso is more reminiscent of hot press paper.
Paint on paper painted over with gel medium will react a bit like yupo paper, the colors are mixing wet into wet and the paint will dry with lots of textures.
On paper painted with gel medium, most edges will dry very defined as you can see on the face here.
Paint on gessoed paper will have a “softer” look as it is possible to soften edges and the paper is still a bit absorbant.
Paintings done on gessoed paper with watercolor will have a softer look, because most edges can be soften.
Paintings on paper painted over with gel medium, are more textured and will show more hard edges.
Lifting off paint from paper brushed with clear gesso or acrylic gel medium:
When paper is painted over with medium, you can very easily life off any watercolor paint with a wet tissue paper and start over as many times as you want to.
With gel medium, some colors will stain the paper and you cannot always go back to the initial white of the paper.
You can also lift color of paper painted over with gesso, but the paint will stain more, a bit like it would on paper.
Ideas to try:
You can try to draw edges of an area with watercolor pencils and then spray your paper with water.
If you over painted over gessoed or gel medium paper, you can try rinsing off the paint under the tap in the sink to remove most of the paint. You will be left with a “ghost image” that you can rework later.
This painting was starting to look overworked, so I rinsed most of the paint away in the sink and started fresh from a ghost image.
How do you like to prepare your paper before painting with watercolors or pastels?