Founded in 1896, the Worcester Art Museum not only boasts admirable collections of European and American painting and sculpture, superb mosaics, some 3,700 Japanese woodblock prints, and the famed John Woodman Higgins Armory Collection—it also houses a celebrated trove of watercolors, which because of their fragility and sensitivity to light are rarely displayed.

Through Sept. 10, WAM is presenting a choice selection of 40 European and American works created between the 1870s and 1950s representing a variety of artistic approaches to this subtle but challenging medium. Organized by

Nancy Kathryn Burns,
WAM’s curator of prints, drawings and photographs, the show features rarely exhibited watercolors by such American luminaries as

Childe Hassam,

Winslow Homer,

Rockwell Kent,

John La Farge,

John Singer Sargent
and

Andrew Wyeth
(his riveting 1957 “The Rope,” a study for “Hay Ledge”). It also includes examples by artists less known for their activity in watercolor and gouache (also called “opaque watercolor”), notably

Amedeo Modigliani,

Gustave Baumann
and

Ernst Ludwig Kirchner.
These newly unboxed paintings range stylistically from Sargent’s bravura brushwork to the deliberate poster-like rawness of social commentator

Jacob Lawrence’s
1943 “They live In firetraps.” Also featured are examples from WAM’s collection of watercolors painted or influenced by members of the San Ildefonso school, a collective of Native American artists working in the Southwest during the first half of the 20th century. Because most of these pieces have so long been safely archived, they are in prime condition, their fragile pigments fresh and unfaded. Moreover, beyond reflecting over 70 years’ progression of watercolor styles, they illustrate a variety of techniques employed by the artists to achieve their effects, some not always obvious to viewers. Informative technical discussions are included in the wall cards.

For example, Childe Hassam’s 1916 “Yonkers From the Palisades,” a panoramic view looking across the Hudson River from New Jersey’s craggy shore, achieves textural contrast between the quick, fragmented brush strokes of the cliffs and their autumnal foliage and his flowing, idealized blue water. To paint the river, Hassam applied layers of blue and yellow-green wash, before tamping them down with a bit of sponge or other absorbent material.

Similarly, Rockwell Kent’s 1926-27 “Boy on Cliff” demonstrates wash manipulated to create a different effect: Here, a lone youth, precariously balancing on a narrow rock outcropping, ponders the sea below. Kent surrounds the boy’s head with a mystic aureole of light against the picture’s glowing polychrome sky. As Ms. Burns observed to me, “he produced that sky by brushing adjacent washes of various hues, and most probably using a similar absorbent material to apply further layers of blue and rose tones.”

Altogether different in mood,

Maurice Prendergast’s
effervescent “Venice” (1911) exemplifies his well-known use of staccato dabs of color with which he recorded the view outside his Venetian hospital window while recuperating from emergency surgery during a painting holiday there. Characteristically, he makes the mosaic-like dabs scintillate by leaving surrounding areas of the cream paper visible.

Not surprisingly, Sargent and Homer are easily the show’s stars. Sargent’s “Muddy Alligators” (1917) is among his most exceptional watercolor essays, painted during a trip to Florida after he had essentially abandoned portraiture for the landscape painting that had long been his great love. Over graphite outlines, he loosely deploys quick patches of watercolor to capture a group of these fearsome reptiles lolling about their swampy habitat. Sargent pools some patches and scrapes away others—notably to form the sharp teeth of the open-mouthed gator in the foreground. Hanging alongside the painting, three of Sargent’s detailed pencil sketches of alligators reveal the intensive preparatory study behind the artist’s apparent spontaneity.

Created during Homer’s second visit to the Bahamas, “Rum Cay” (1898-99) shows a muscular Bahamian running past a large sea turtle against a minimal beachscape comprising three spare horizontal bands of color wash. Apart from the oblique reference to Aesop’s tortoise and hare, the runner bespeaks Homer’s consummate skill at capturing the athletic human body in action, from the splendid delineation of the man’s face and sunlit torso to the flexed toes of his left foot.

In contrast, Homer’s “Old Friends” (1894) conveys the deep emotion of a rugged old woodsman contemplating a massive ancient tree. Homer’s expressive rendering of the man’s upturned face underscores the emotional link. The composition illustrates his use of “subtractive” painting: Though Homer evidently depicted the Adirondack woodland surrounding the man and the enormous trunk, he subsequently scraped away the paint at the left of the sheet, fashioning a br ight white cloud out of the white paper’s now roughened surface to emphasize the great tree’s majestic presence. Having first seen this profoundly moving work when it was lent by the WAM, along with Sargent’s “Muddy Alligators” and “Bathers,” to the 2017 show “American Watercolor in the Age of Homer and Sargent” at the Philadelphia Museum of Art, I can declare on seeing it this time that familiarity certainly has not bred contempt.

—Mr. Scherer writes about music and the fine arts for the Journal.