All kinds of surfaces are fair game game to paint on. I have painted on smooth hot-pressed, mild-textured and rough paper. In addition, I have painted on soft press paper and bristol board.
This was painted on a remnant of Arches 300lb watercolor paper that I received communicating a Christmas gift. I have read where this paper is recommended for plein air painting or direct painting. Also, it dries slower than thinner papers allowing the artist more time to work their washes. As a side note, I have begun experimenting with gum arabic which gives you some control over the painting process.
I like the added touch of venetian red on the middle left in contrast to the cooler pigments.
