MANUFACTURE OF MinK PowDER 279 
spread on trays or other similar containers, and dried to a hard 
substance in vacuum chambers or in other vaults or drying ap- 
paratus, provided with heating devices or currents of hot air. 
The dried product is subsequently ground to a fine powder. 
Examples of this type of milk-drying processes are the Wimmer 
process, the Campbell process and others. 
The Wimmer Process.—The milk 
is boiled in a vacuum pan similar to 
that used in the manufacture of con- 
densed milk. The vacuum pan has a 
deep steam jacket for heating, but in 
the place of the usual coils, the pan is 
equipped with a mechanical stirrer. 
The milk is condensed at a relatively 
low temperature and the stirrer re- 
volves until the water content of the 
milk is reduced to about 30 per cent 
and the milk has become porous and 
crumbly, though it still forms a com- 
pact mass. The drying is then com- 
pleted in the open air and without addi- 
tional heating. The product is then 
eround to a powder. This is the pro- 
Hip? OO ede mashing  eees invented by Ole Bulk Wimmer: of 
Copenhagen, Denmark. 
The Campbell Process.—This process was invented, pat- 
ented and improved by J. H. Campbell of New York City, U. S. 
patent Nos. 668,159 and 668,161, February 19, 1901; U. S. patent 
No. 718,191, January 13, 1903; U. S. patent No. 762,277, June 
14, 1904; and by J. H. and H. C. Campbell, U. 3. patent No. 
668,162, February 19, 1901; and by C. H. and P. T. Campbell, 
U.S. patent No. 771,609, October 4, 1904. 
The Campbell process consists essentially of concentrating 
milk to a high degree of concentration by blowing heated air 
through it in an open vat. The milk is reduced to a very thick 
consistency, resembling a batter. The concentrated milk is then 
removed from the evaporating tank, is reduced mechanically to 
small units by means of a pugging or shredding machine, or 
