84 Milk and Its Products 
amounts of butter so made were of inferior com- 
mercial quality, could not be mixed with the whole 
mass of butter, and entailed a considerable loss 
upon the creamery. 
The oil-test churn was an outgrowth of this 
method, intended to remedy its defects, and was in 
a great measure successful. In operating the oil-test 
churn, the individual samples taken from each patron 
were very much smaller, and were taken in small 
glass tubes. These tubes were put in a frame and 
agitated until the fat was drawn together in a solid 
mass ; the tubes were then immersed in water suf- 
ficiently warmed to melt the fat, and when so 
melted the fat would float upon the surface of the 
liquid in the tube. The tubes were allowed to 
become cool, were then a second time agitated to 
churn any particles of fat that had escaped the 
first churning, and the fat remelted; it then ap- 
peared in the form of a clear layer of liquid upon 
the top of the contents of the tube, and could be 
readily measured. The proportion of melted fat 
so obtained was taken as a measure of the butter 
value of the cream of which it was a sample. 
This test was generally used in cream-gathering 
factories, and was a very fair measure of the 
butter value of the cream. There was always a 
portion of the fat remaining unchurned, but in 
cream it was a small percentage. In milk, how- 
ever, it was a much larger proportion, and the 
oil-test churn was never successfully used for de- 
termining fat in milk. 
