The term "stoneware" refers to the heavy-duty, nonporous pottery jugs, jars, and crocks made from the early 1700s through the late 1800s. Watertight and nonreactive to acids, these somewhat clunky vessels were used every day, whether as jugs for beer, cider, and vinegar or as storage crocks for butter, jams, and pickled vegetables. Other forms include butter churns, batter pails, inkwells, mugs, bowls, and pitchers. Today widemouthed vessels are often used around the house as jardinieres, kitchen-utensil holders, or umbrella stands. The very best pieces stand alone as prized folk-art icons.

WHITE CLAY, BLUE BIRDS

The most durable vessels were made of kaolin, a white clay that vitrifies under extreme heat. The clay was found mostly in New Jersey and New York. Potters elsewhere imported the precious white stuff, often supplementing it with local red clay, resulting in a more porous product. During firing, pieces were finished by throwing rock salt into the kiln to produce a glossy, mottled surface - hence the term "salt-glazed."

Early pieces were sometimes incised with a pointed instrument and highlighted with cobalt blue-tinted slip, a liquid clay that hardens when fired. By the 1840s, incised decoration was largely supplanted by more fanciful blue slip designs applied with a brush, poured from a slip cup, or stenciled. Popular images included birds and flowers. Less common were houses, insects, roosters, vegetables, and patriotic motifs, particularly eagles and flags. Rarer still were human figures, ships, and exotic animals. In addition, the interior of some vessels was coated with dark-brown Albany slip to help make the vessels even more impervious to leaks.

WHAT TO LOOK FOR

In the early to mid-1800s, makers' marks, including the potter's name and location, as well as capacity numbers were often stamped on the sides of vessels and brushed with blue slip. Sometimes even a manufacturing date was scrawled in large script. All markings add value to a vessel because they help identify its origins.

Stoneware is one of those rare collectibles for which flaws add to the appeal and value. They attest to the crude and unpredictable conditions under which wares were made. Uneven firing temperatures, collisions in the kiln, and impurities in the clay produced interesting results: lopsided silhouettes, uneven tops, burn marks. One of our favorite pieces is an early-19th-century John Remmey jar from New York City that is completely misshapen. But be wary of questionable workmanship. If the blue decoration is more faint than brilliant, or appears to be on top of the glaze rather than under it, the piece might be doctored. Potters decorated their wares before salt glazing, not after. You can actually scratch new paint off the surface with your fingernail.

If you're just beginning to collect, a cylindrical crock with no decoration can be found for under $100. However, we urge you to stretch a bit and get one with some blue detailing. Typically the more surface area the decoration covers and the rarer the motif, the more the piece is worth. Simple floral or bird patterns go for between $500 and $1,000. On the other end of the spectrum, an 1870 preserve jar from Buffalo, New York, with an elaborate rooster motif recently sold at auction for $34,000.

As for that Cushman crock, we were delighted to sell it for $2,000 just before we went to college. But the real thrill, as any collector can attest, was finding it in the first place.