One of the main requirements for a successful ice cream business is uniformity of quality. In order to obtain this, it is necessary to have cream each time containing the same percentage of fat. As it is impossible to always get cream of a uniform fat content, the cream must be standardized. That is, the percentage of fat must be either increased or decreased to the desired amount. It is the usual practice to have richer cream than is to be used and reduce it by the addition of less rich cream, whole milk, or skim milk. If the cream was lower in percentage of fat than was desired, it could be standardized only by the addition of richer cream. Prof. R. A. Pearson has devised a very simple method, known as the rectangular method of standardization. This method is as follows: draw a rectangle and place in the center the percentage of fat desired. At the left hand corners place the percentages of fat in the materials to be mixed. It is customary to place the larger figure at the top, thus: [Illustration] Then subtract diagonally, placing the remainders at the right hand corners, as shown above. These show the proportions by weight in which the materials must be mixed to give the desired percentage of fat. A problem may serve to illustrate the method. How many pounds each of 30% cream and 4% milk are necessary to make 260 lbs. of 20% cream? [Illustration] This shows 16 lbs. 30% cream and 10 lbs. 4% milk make 26 lbs. of 20% cream, but 260 lbs. is required. This is best solved by simple proportion: 10 lbs. milk∶ 26 lbs. 20% cream∷ x lbs. milk∶ 260 lbs. 20% cream. Solving x = 100 lbs. 4% milk required and 260-100 lbs. milk = 160 lbs. 30% cream required which may also be determined by proportion. To be sure no mistakes are made in figuring, it is best to prove all standardizations. The proof is simple. 260 lbs. 20% cream contains 52 lbs. fat (required). 160 lbs. 30% ” ” 48 lbs. ” 100 lbs. 4% milk ” 4 lbs. ” — Making a total of 52 lbs. fat, the amount required. In the above problem a definite amount of the mixture was required. There is another class of standardization problems in which the amount of one of the materials is given, to find the quantity of the other required to standardize it: How much 4% milk must be mixed with 420 lbs. of 40% cream to make a mixture testing 25% fat? [Illustration] This shows that 15 lbs. of 4% milk will standardize 21 lbs. of 40% cream to a cream tasting 25% fat. But there are 420 lbs. of 40% cream to standardize. By simple proportion, 15 lbs. 4% milk∶ 21 lbs. 40% cream∷ x lbs. 4% milk∶ 420 lbs. 40% cream. Solving x = 300 lbs. 4% milk 420 lbs. cream + 300 lbs. milk = 720 lbs. 25% cream. Proof: 720 lbs. of 25% cream contains 180 lbs. fat. 300 lbs. of 4% milk ” 12 lbs. ” 420 lbs. of 40% cream ” 168 lbs. ” ——— Making a total of 180 lbs. fat.