88 DAIRY LABORATORY GUIDE 



EXERCISE 6 



CHANGING THE CREAM SCREW ON THE SEPARATOR 



Object: To determine the effect of adjusting the screw 

 upon the variation in percentage of butter-fat in the cream 

 and in the skimmilk. 



Apparatus: Separator, milk, containers, scale, sample 

 bottles, thermometer, and testing outfit. 



Steps: 1. Assemble the separator, temper the milk to 

 85 F., and weigh out three lots of a definite amount each. 



2. Separate lot No. 1 with the screw in a normal 

 position; then determine the weight of the cream and the 

 skimmilk and retain samples to test. 



3. Adjust the screw slightly so as to increase the per- 

 centage of butter-fat in the cream 5% above normal. Sepa- 

 rate lot No. 2, determine the weight of the cream and the 

 skimmilk, and retain samples to test. 



4. Adjust the screw so as to decrease the percentage 

 of butter-fat in the cream 5% below normal. Separate 

 lot No. 3, determine the weight of the cream and the skim- 

 milk, and retain samples to test. 



5. In this exercise care will be necessary to note whether 

 the adjustment is done by means of a cream screw or a skim- 

 milk screw. The amount of adjustment will be determined 

 by the position and character of the screw. 



Application: 1. Compute the amount and the value at 

 current prices of the butter-fat lost in one year in 10,000 Ibs. 

 of skimmilk when the percentage of loss is normal. 



2. How do the screws in different makes of separators 

 compare as to the amount of adjustment required to obtain 

 the same results? 



3. In skimming, what percentage of cream does the sep- 

 arator in hand do the most efficient work? 



