Traditional Chinese Water-Seal Jars

The water-seal pickle jar is one of the oldest pieces of fermentation technology still in everyday use, traditionally made in glazed pottery for Sichuan paocai and northern suan cai. The mouth has a moat around it; the lid sits down into the water-filled moat, and that ring of water becomes an airlock.

Rendering it in glass keeps the elegant self-regulating seal but lets the cook watch the ferment — bubbles, brine clarity and vegetable color — which is impossible in opaque crockery.

Sichuan paocai, suan cai and fermented greens, lacto-fermented vegetables, brined pickles and kimchi, plus home and restaurant fermentation projects generally. The larger 3–5 L sizes serve restaurant prep and serious home fermenters.

It is bought both as a working ferment vessel and, increasingly, as an attractive countertop piece for the fermentation-curious.

The defining feature is the circular moat molded around the mouth and the inverted dome lid that sits in it. Water poured into the moat seals the lid: fermentation gas bubbles out through the water, but outside air cannot get back in. No rubber gasket is needed.

Glass thickness around the moat and lid is designed for repeated handling, and the lid is shaped to seat reliably in the channel.

Keep the moat topped up with clean water throughout the ferment — if it dries out, the seal is lost and air gets in. Leave headspace for the brine and gas, and keep vegetables submerged under the brine. The jar is not pressure-rated; it works precisely because it vents.

Clean the moat and lid between batches, and avoid thermal shock; ferments run at room temperature, so the glass is rarely stressed by heat, but the large sizes are heavy when full and need careful, level handling.

The body and the dome lid are press-and-blow formed; the moat channel around the mouth is the distinctive molded feature and must be formed cleanly to hold water. The two pieces are matched so the lid seats in the channel.

Annealing matters on these large, thick vessels to relieve stress, and the moat and lid fit are checked so the water seal works as intended.