The first essential component for a good watercolor painting is a good piece of archival paper. Generally, there are three types of Paper Available; Hot Press, which has a very smooth surface; Cold Press, which provides a medium texture (my personal favorite); and Rough which is characterized by a deep texture.
I prefer heavy, thick 300 weight paper; it does not warp or require any preparation.
Lighter 140 Weight paper requires stretching, over a board using Yes brand glue to adhere the paper to the board ; but you must weight the paper down quite heavily until completely dry.
In the past I used Watercolor Board, which is no longer being made; at least to my standards. So I had to make my own board from Masonite covered by watercolor paper, glued down with Yes brand glue; an archival glue that bonds the paper to the board.
I usually glue down one layer of paper, allow it to dry, and then attach a second layer, and dry again. This gives me a suitable surface for my paintings.
This technique is used for paintings larger than 40×60; since that is the largest size of 300 weight paper I can find. But the paper is also available in rolls that are 52 inches wide, ten yards long, enabling me to create a larger watercolor paintings.
This process can require lots of time, effort and space to create a large painting and almost all sizes will require wooden bracing on the back. The gluing process will require using a roller to smooth out the glue and many weights to allow the paper to adhere uniformly to the board.
This will result in a solid surface which will not warp; exactly what you will need to compose a good watercolor painting.
