A dozen years ago or so, the Penobscot Marine Museum in Searsport mounted a remarkable show devoted to sailors’ valentines. In addition to exploring the history of this folk art – and debunking the myth that sailors actually made these ornate shell souvenirs – the exhibition featured a group of contemporary practitioners, most notably, Grace Madeira.

A resident of Wayne, Pa., with lifelong family connections to Mount Desert Island, Madeira has had a varied artistic career. After graduation from a Boston art school, she mastered bronze stenciling and portrait restoration. At one point she painted designs on helmets for some of the pilots flying out of Otis Air Force Base near her former home on Cape Cod.

In 1970 Madeira turned to collage, decorating antique seabird prints with seashells and natural fibers and grasses. She made her first sailor’s valentine in 1979, as a gift to her husband. Since then Madeira has become one of the foremost artists in the field, which experienced a revival in the 1960s and continues to go strong today.

Now Madeira and three other shell artists have published “Sailors’ Valentines: Their Journey Through Time” (Schiffer Publishing, 160 pp., $45). The richly illustrated book traces the evolution of this unusual art form, from its origins in England (where shops stocked shells brought back from the Pacific) to the cottage industry that arose in Barbados to modern-day activity.

Reached by phone, Madeira noted that the earlier valentines appeared to have been made using the same pattern, typically a heart and a motto (“Forget Me Not”) within a shell mosaic encased in an octagonal box. Today’s artists, she reports, have “taken off” with their own designs. A greater variety of shells are available, although she notes with concern that certain specimens are becoming increasingly scarce.

Madeira starts each design at the center and creates an elaborate diagram that guides the development of the piece. She uses water-soluble glue that allows her to remove a shell if it doesn’t fit right. Depending on the intricacy of the design, a sailor’s valentine may take her 40 to 50 hours to complete. She often has to live with the design for many weeks before it is resolved to her satisfaction.

“Playing with colors, lights and darks, sizes and shapes – all of those factors come into the design,” Madeira reports. She makes her own frames, sometimes enhancing them with stain or spongework to set off the shells.

Madeira has shown her work in galleries and museums on the East Coast, from Palm Beach to Maine, but these days she only does custom work. A new mosaic piece inspired by a Persian rug will be displayed at the annual Philadelphia Shell Show at the Academy of Natural Sciences in October.

For her appearance at Port in a Storm Bookstore in Somesville, Madeira will have on hand one of her sailor’s valentines, a marvelously symmetric and complex kaleidoscope incorporating many different shells, from coquinas to purple-top cowries. As she notes, it’s one thing to admire a valentine reproduced on a page, quite another to have the object in front of you in all its multifaceted glory.

Grace Madeira will sign copies of “Sailors’ Valentines: Their Journey Through Time” at Port in a Storm Bookstore at 4:30-5:30 p.m. today. Call 244-4114 to confirm time and date.