I discovered watercolor encaustic quite by accident. One spring I was struggling to get more refined detail in a cherry tree painting. I could not get the wax crayons to work well enough I decided to try oil paint. I really do not like oil paint and, to keep my interaction with that material to a minimum, I did a watercolor under painting on the canvas with a plan to do a light wash of oils on top of it to make it permanent. When I finished the water color I did not want to change it in the least.
Then the thought occurred to me that maybe clear melted wax would work as a sealant. (You cannot put varnish on top of watercolor because it is liquid and anything liquid will dissolve the watercolor.) I melted wax in my fry pan palette and then got out a brush and a hair dryer. I heated the painting with the hair dryer and started to apply the wax.
It worked. The watercolor paint was totally inert to the application of the wax, and, the colors took on an even more brilliant glow than before.
I was lucky with that first attempt. The pre-primed canvas I used just happened to be semi-compatible with watercolor paint. Other canvases I have since tried repel watercolor. The watercolor just floats on top of the canvas. It does not work.
Pre-stretched canvas would be so easy to get, but, it does not work because the sizing and priming agents used are geared for oil and acrylic, and completely repel watercolor paint. I did a few tests on organic cotton, portrait grade Belgium linen, cotton Army duct, and heavy weave plain cotton fabric.
I applied pure wheat starch to a swatch of each and then a combo of wheat starch and kaolin clay.
Ancient Art Materials - Watercolor Encaustic
Wheat starch and kaolin clay on Army duct. Less bleed and more control of brushwork possible.
Wheat starch on Army duct.
Very conducive to wash-like effects. Has a lot of bleed.