I am an artist who works primarily with transparent watercolors and I would like to share with you, some interesting facts about its history.
Water-based pigments have been in use for a very long time, for example: illuminated manuscripts of the Middle ages, and the existence of many schools of watercolor painting in the Near and Far East.. From the 16th century however, as Western European countries grew in power and extended their reach to distant unexplored lands, they needed a visual record of the flora, fauna and "natives" of new countries. Until then, one of the uses of watercolors had been to tint topographical drawings and early maps. It was a very portable medium and therefore a convenient one for naturalists and/or artists who were willing to brave the hazards of travel in those days to produce illustrations of exotic lands.
In the following centuries as a recording tool, watercolor became popular as well with scientists, anthropologists, botanists and other professionals. Especially as the quality of paper supports and paints improved with time.
In spite of it's increasing popularity however, watercolor paintings were not considered important enough to be serious art. They were regarded as tinted drawings. The status changed when artists began using it in a more painterly style. The emphasis shifted from topographical accuracy to pleasing "point of view" and "atmosphere".
As a result, one of the high points in watercolor history occurred in the 19th century when a whole school of British watercolor painters was established. Foremost among these artists was J. M. W. Turner. His watercolors especially, influenced generations of artists to come and helped establish the basis for what we know today as watercolor.
The following late 19th and early 20th century saw American painters such as Winslow Homer and John Singer Sargent creating virtuoso watercolors of unsurpassed technical quality. Their influence can be seen today in the works of many current painters who work with the different forms of the medium.
The appeal of watercolors to both the amateur and professional lies in the fact that though it can be difficult at it's highest levels, one can easily learn to create pleasing paintings with the medium. Among amateur watercolorists, Prince Charles continues a family tradition. His ancestor Queen Victoria was addicted to watercolor and received instruction from the painter and writer, Edward Lear.
There are two main types of watercolors, transparent and opaque. For design work when ease of correction is required, opaque watercolors or gouache is preferred, for example: all forms of illustration, textile and paper product design etc. Many contemporary artists have effectively mixed it with other mediums, pastels especially, creating textures and other qualities that extend our understanding of it's possibilities.
(*The primary source for the brief history was from: Finch, Christopher. "19th Century Watercolors" Abbeville Press Inc. 1991)
Of general Interest:
A few of the artists I often refer to are: Joseph M. William Turner, Winslow Homer, Charles Demuth, John Singer Sargent, Maurice Prendergast, John Marin
Many artists, past and present have used watercolor in a variety of ways. As a sketching tool, for preliminary studies, to experiment with etc. I would recommend reading books on specific artists that appeal to you.
For art Instruction:
Many books for Beginners and Advanced students in Watercolor Techniques are to be found in bookshops and libraries. These are only a few of those available.