Beer - Sailing The Coolship
In the course of your reading about brewing you may have run across the term, "coolship." Some of you may have wondered, "what the heck is a coolship anyway?" No, it's not a boat full of guys dressed in chav duds. A coolship is a flat, open vessel traditionally used to cool hot wort and allow hot trub to settle out. Although more advanced methods of cooling and trub separation have been developed over the years, the venerable coolship is still used in a handful of small breweries that cling to tradition.
Prior to the advent of refrigeration and the use of ice in brewing, the coolship was the sole means of cooling hot wort. As a home brewer in the modern era, it is hard to comprehend the difficulty of such a task. It takes long enough to cool five gallons of hot wort to pitching temperature, even with a cold water bath. Imagine trying to cool several barrels of near boiling wort using only the temperature differential between the wort and the atmosphere.
But, that's how they did it in the days before refrigeration and other more sophisticated cooling methods were developed. The coolship, or, surface cooler as it was known in America and England, was specifically designed to take advantage of the only means of cooling that existed. A shallow (8 - 14 inches deep), rectangular vessel with a length and width much greater than its depth, the coolship maximized the surface area of the wort. Thus more wort was exposed to the air. This facilitated cooling through loss of heat to the cooler air above the hot wort.
Originally made only of wood, they were later lined with iron or copper. Eventually, iron, copper and stainless steel replaced wood as the materials of choice. Brewers in England and the U. S. were quick to accept the more sturdy and durable iron coolers. German brewers, however, were more reluctant, as they were concerned that oxidized iron would cause the wort to darken. Some brewers were also worried about the effect of electricity generated during thunderstorms on wort in iron coolers. They soon found that wort tannins react with iron to form a coating that protects the wort and also protects the iron from rust. New iron coolers were "seasoned" before the first use by filling them with a tannin solution (tannic acid).
Coolships were traditionally situated on the top floor, where louvered walls permitted good air circulation. This allowed some of the steam to escape and the cooler outside air to enter. Later, large fans were typically mounted over the coolship to facilitate air movement and the escape of steam. It was not uncommon for a brewery to have two to four coolships. Early brewers often made multiple beer styles from a single brew, with each style requiring a different cooling regime.
Even with a wort depth of only two inches, in cool weather it took six to seven hours for the wort to cool to 59 degrees F. When the air temperature was hot, the process could take from 12 to 15 hours. For lager beer, common practice was to allow wort to stand in the cooler for at least five, but no longer than, 12 hours. This procedure allowed sufficient time for trub to settle - an important factor in beers where maximum clarity was desired - but protected against fermentation by wild yeast and bacteria.