No, generally you cannot use acrylic varnish on oil pastels.
Why Acrylic Varnish is Not Recommended for Oil Pastels
Applying acrylic varnish over oil pastels presents significant compatibility issues due to the fundamental differences in their composition and drying properties. According to the provided reference, there are two main reasons why this combination is problematic:
1. Incompatibility: Water-Based vs. Oil-Based
- Acrylics are water-based. Their primary medium is water, which evaporates as they dry.
- Oil pastels are oil-based. They use a non-drying oil as a binder.
These two types of mediums don't mix well. Applying a water-based material like acrylic varnish over an oil-based surface can lead to poor interaction and adhesion problems.
2. Non-Drying Nature of Oil Pastels
Unlike many art materials that cure or harden completely over time, oil pastels never fully dry. Their binder is a non-drying oil, meaning the surface remains somewhat malleable and receptive to disturbance.
The Result: Poor Adhesion and Peeling
Both the incompatibility of the water and oil bases and the persistent non-drying nature of the oil pastels contribute to a critical issue:
- The acrylic varnish is not going to adhere well to the oily surface of the oil pastels.
- Over time, this lack of proper adhesion means the acrylic layer may peel off, compromising the integrity and appearance of your artwork.
For these reasons, using acrylic varnish on oil pastel artwork is not a stable or recommended method for protection or finishing.
