Traditional gesso is sold as a powder, which is mixed with water in a 4:3 ratio, covered and allowed to soak for a day before warming it to melt the glue. Warming produces a texture like melted ice cream. The liquid is then painted on, allowed to dry, sanded, and painted on again.
After the first coat, I found that the remaining gesso cooled to a bubbly, rubbery texture that could be ground into the preceding layers, squishing it into a smooth paste in the process. Both wet and dried gesso is a stark, eggshell white.
The next step was to mix and apply the powdered milk paint. This is a sample of Real Milk Paint Co.'s "barn red," which has a slighly dull, ochre-like color (though if I use this type of paint on a large scale, I plan to use a colorless base and add storebought pigments so I know they're authentic). I mixed it up in a common salad dressing-style cup with a lid and used another cup to measure out the water, as the recommended ratio of powder to water is simply 1:1.
Not long after the paint was applied, most of the gessoed swatches showed fine cracking. Presumably the gesso absorbed water from the paint and swelled. The swatches with glue but no gesso didn't seem to have this problem.
Interestingly, the swatches that were neither soaked in glue nor gessoed seemed to do very well, with no cracking even when I tried poking at them with my fingernail. This may change over the following month if the curing paint becomes harder and more brittle. The other factors are how well it handles water damage and whether the paint over chamois can be sufficiently sealed with wax if water becomes a problem: a hard, non-sticky wax may also tend to flake off if the underlying leather is still puffy.
