John Singer Sargent's approach to watercolor was unconventional. Going beyond turn-of-the-century standards for carefully delineated and composed landscapes filled with transparent washes, his confidently bold, dense strokes and loosely defined forms startled critics and fellow practitioners alike. One reviewer of an exhibition in London proclaimed him "an eagle in a dove-cote"; another called his work "swagger" watercolors. For Sargent, however,...