The definition of varnish is 'a transparent, hard, protective finish or film primarily used in wood finishing but also for other materials.' So the protective finish for acrylics is a coat or two of protective finish. The brand I settled on is Mixwax Polycrylic, Satin Finish.
Acrylic paint dries to a porous finish which attracts dust and dirt. Different brands, colors and even viscosity can produce differences in gloss that can be very unattractive. Varnish solves these problems by giving a hard, transparent coat that unifies the finish.
Given those good reasons to varnish, I was totally unprepared for how great it made the paintings look. Colors are intensified, textures are enhanced and the finish is slightly glossy and beautiful.
The Adventure continues...