CHURN (.1„5. (writ', Icel. kirna, Dam kj(erne, churn, dialectic Ger. Kern. Nleel. Avarna, cream). A machine for agitating milk or cream, for the production of butter. The principle of the operation is considered in the article on BurrEit-MAKINn (q.v.). Mere stirring of the cream, it continued long enough, will bring butter; and agitation of the by means of bubbles of air passed through it will accomplish the same result. The oldest form of churn was the upright or plunge churn. This was labori ous, and was superseded by the dash churn, and by a form in which the cream was agitated by 111V:111S of floats or paddles. There were many kinds of these, with arrangements for cooling or heath the cream. But these injured the texture of the laitter, because of the effect of the stirring motion on the grain of the first particles of butter fanned. Barrel churns and rectangular churns, hung upon the lower or the shunter axes, have conic into very general use, and box churns which are oscillated, often called swing churns, are much used. especially in small dairies.
The best churns are entirely hollow vessels of the barrel or box shape, which agitate the cream through concussion of the particles upon the sides of the churn. The churn should not
be entirely filled; it should be left half, or pref erably only one-third. full. Although the yield of butter is not much diminished by increasing the amount churned at one time, the time re quired for churning is increased, and the tem perature is raised at the end of churning, which is decidedly injurious to the butter, mak ing it softer and more difficult to handle. The speed of the churn is an important factor, in point of both time and completeness of churn ing. Too rapid churning gives the cream the motion of the churn, and the particles of butter fat are not brought into contact with each other. The labor of churning has been very greatly decreased in the modern churn, and forms have been made in which dog-power, horse power, and steam-power are employed. The power (1111111S, of immense size, are usually em ployed in creameries. The combined churn and butter-worker has been described under BuTTER Womuat (q.v.). The butter-extractor is essen tially a cream-separator and continuous churn combined. The bolter made with this machine is, of course, sweet-cream butter.