My eldest brought home one of my favorite artworks of hers from last year, an ephemeral glimpse of a mythical beast on a moonlit hill. As she got in the car she announced: "Do NOT touch the hill!" She did the canvas in mixed media, and the hill was pastels and was rubbing off on anything it touched! I assured her we could fix it, as I had a can of clear spray at home. First coat looked good, so I followed directions for the subsequent coats. An hour later, to my horror, a film of white bloomed across the painting. My eldest was very chill about it, but I felt awful. We tried to rub it off with a bit of water, carefully avoiding the watercolor trees, which looked great, until it dried. We also tried using a hot hair dryer in case the bloom was from humidity. No change.

White bloom on a black acrylic painting caused by an aerosol clear coat

Rather than risk anymore unexpected changes, I made up a test canvas by painting it with acrylic then spraying it with the same clear fixative. There was a light white bloom, so we used that to test putting a layer of Modge Podge over it.

Test canvas with black acrylic and clear coat, Modge Podge tested on the edges

It seemed to work, so I did the same treatment on the canvas. It did not remove the white. But, the way the white happened on the canvas, it made it look like a tattered fog, and intentional. Lessons learned: applying a clear coat to a mixed-media art project is fraught with peril, especially for dark colors. If faced with the situation again, I would purchase a high end fixative and spot check. If doing my own mixed media piece, I would make a waste canvas with the same selection of media for testing.

White bloom caused by a flat crystal clear coat spray
Mixed media mythical beast by my eldest; acrylics, pastels, watercolors, cut paper, embroidery on canvas, as displayed at school