Good watercolor paper is an absolute necessity! It is more important than
the watercolor paints, or the brushes, or any other item in your kit!
Cheap watercolor paper---especially paper containing any wood
pulp---will neither take the paint attractively nor last. In fact, wood
pulp paper will self-destruct from its own acids in short order.
Good paper is one hundred percent rag content. There are a number of good
brands, mostly made abroad. I think it is safe to say that the most
popular---worldwide---is "Arches," made in France. It is certainly the
most available brand in good stores and mail order houses. I use a seven
inch by ten inch "block" of twenty sheets in 140 pound weight. A "block"
is a number of sheets glued together at the edges with a hard backing
board, and is very convenient for this kind of painting. After the
painting is dry, the sheet can be separated from the block by slitting
the glued edge with a knife.
The "140 pound" weight is a measure of the thickness of the paper, which
is really the thickness of light cardboard. This size and weight will
not buckle or ripple significantly when wet. Anything larger should be
stretched to give a smooth surface for painting---so I would recommend
this size and weight.
I cannot emphasize strongly enough that your paper is the most important
part of your equipment, and will in large part determine the quality of
your resulting painting. Good paper is not cheap---but for a block of
twenty sheets you are only paying about one dollar a sheet. So don't
skimp on this item. And your sketch will last nearly forever if you
happen to turn out a work of art. Experiment with other good papers to
suit your taste, but make sure they are one hundred percent rag paper
with a pleasant surface for painting. Start with the finest paper and
avoid the "student" grades.
Watercolor paper comes in three surfaces: "rough," "cold pressed," or "hot
pressed." Rough is fine for larger paintings---but in my estimation too
rough for small paintings. Cold pressed is a medium surface perfect for
our purposes. At least start with cold pressed paper. Hot pressed paper
is very smooth and usually not chosen for watercolor paintings.