CREAMERY CALCULATION. 107 
The same mistake is also likely to be made in finding 
the average test from several creamery-plants and skimming- 
stations. 
Calculation of Overrun.—The amount of overrun is the 
difference between the amount of pure butter-fat, and the 
amount of butter manufactured from that given amount of 
fat. This difference, divided by the amount of fat and multi- 
plied by 100 will give the percentage of overrun. The calcu- 
lation of the overrun in the creamery should always be made 
Fic. 64.—A Cheshire creamery, England. (London Creamery Journal.) 
from the fat-basis on which the patrons are being paid. If 
the fat is delivered in the cream, the overrun should be calcu- 
lated from the fat in the cream. The overrun calculated from 
the composition of the butter manufactured would not be an 
indication of the correct overrun, as there might be serious 
losses of fat sustained during the different steps in the manu- 
facture, such as from inefficient skimming, incomplete churning, 
and general losses in the creamery. It is possible that butter 
might show a high content of the substances not fat, and 
yet not show a good overrun on account of losses; while butter 
containing only a medium high moisture-content might show 
as great or greater overrun on account of thorough and efficient 
work during the different steps of manufacture. 
