(1) Remove flask from holder and run 4 cubic centimeters water (one charge on water burette) into each flask. Be careful not to add more. Shake well until all of sample is mixed with water. This can be done without inserting cork.

For sweetened condensed milk, if not diluted with water, add 8 cubic centimeters of hot water with a pipette. To get hot water, place fat dish filled with distilled water upon solids plate. If sweetened milk has been previously diluted with water and a 10 gram sample has been used, it is not necessary to add water. It is very necessary to shake the flasks containing the sweetened condensed milk very thoroughly after the addition of each reagent. Sweetened condensed milk requires more shaking than any other liquid milk product.

 (2) Before replacing flask into holder, add 1¹⁄₂ cubic centimeters C. P. ammonia, one charge on burette. Shake well so that all of sample is well mixed with ammonia. This can be done without inserting cork.

 (3) Add 10 cubic centimeters of 95 per cent alcohol. Insert cork, twisting cork in firmly, using best quality corks only. Replace the flask into flask holder. Shake thoroughly, and see that no milk adheres to any part of flask undissolved. In case particles of milk stick to side of flask, shake thoroughly until these are washed away. It is of utmost importance to shake thoroughly at this point.

 (4) Add 25 cubic centimeters ethyl ether, insert corks and shake vigorously, lengthwise of flask, with liquid in large bulb of flask, and small bulb extended upward. Stop shaking at end of five seconds until all liquid has run into large bulb and repeat vigorous shaking for four five-second periods.

 (5) Add 25 cubic centimeters petroleum ether and shake in same way.

 (6) Place extraction flasks into centrifuge and whirl for thirty turns at speed of about 600 revolutions a minute. Have centrifuge balanced with small oil sample bottles furnished with tester. Double time for sweetened condensed milk.

 (7) Place four 3¹⁄₂ inch dishes in line on shelf adjoining hot plate, keeping them in order in which their weights were posted on record sheet. Aim to have numbers on flasks correspond with number of dishes.

 (8) Pour ether extraction above dividing line into proper dishes and slide dishes over onto hot plate which should be held at a temperature of 135 deg. C, as indicated by thermometer inserted in nickel plated mercury well. Be careful to pour off no solid matter. Cover dishes with hood.

(9) Repeat the extraction, shaking first to prevent formation of  precipitate, then adding successively 5 cubic centimeters of 95 per cent alcohol, then 25 cubic centimeters ethyl ether and then 25 cubic centimeters petroleum ether, and shake vigorously after the addition of each of above three reagents for four five-second periods.

(10) Whirl in centrifuge for thirty turns.

(11) Move aluminum dishes back upon shelf adjoining hot plate, when almost dry, and pour the second extraction into proper dishes. Never pour extraction into hot dish. Remove dish from hot plate as soon as ether is all evaporated.

(12) When all of ether has evaporated, place dishes into vacuum oven which should have a temperature of 135 deg. C. Keep them there for five minutes after the vacuum gauge shows at least 22 inches of vacuum.

(13) Place dishes into cooler for seven minutes, with pump outfit running. See that water is running through cooling plates.

(14) Place counterpoise for dish and the approximate weight for fat on right hand balance pan.

(15) Transfer dish to left hand balance pan and weigh quickly to 0.10 milligram (0.0001 gr.).

(16) Weight of fat divided by weight of sample taken, multiplied by 100 represents percentage butter-fat.

 (1) The temperature of the hot plate in the solids vacuum oven must be 100 deg. C. The temperature of the outside solids plate must be 170 deg. to 180 deg. C.

 (2) To weighed milk in solids dish, add about 1 cubic centimeter water and distribute mixture evenly over bottom of dish, immediately after weighing. For sweetened condensed milk, use hot water, or place momentarily on hot plate and distribute evenly over dish by shaking sidewise very carefully after cold water is added.

 (3) Place not more than two dishes at once upon hot plate, which must be perfectly level. Allow all visible moisture to evaporate. During the evaporation turn the dishes around with crucible tongs slowly so as to produce an even boiling over the whole bottom surface of the dishes. The dishes must be watched carefully during the evaporation. This step should require not more than two minutes. The end point is reached when bubbling and crackling ceases and sample shows first trace of brown. Vigorous boiling without spattering and complete evaporation are fundamentally essential.

 (4) Place dishes into vacuum oven which must be at 100 deg. C. and turn on the vacuum. Heat for ten minutes. In the case of sweetened condensed milk keep it for ninety minutes in vacuum oven, or heat for twenty minutes and deduct 30 per cent from result. The gauge should register not less than 22 inches of vacuum. If for any reason you cannot obtain at least 22 inches of vacuum, then leave your dishes in oven for twice the regular time.

 (5) Remove from oven and place into cooler. Allow dishes to cool for five minutes.

 (6) Weigh dishes with covers on, being careful to weigh quickly and very exactly.

 (7) Weight of dry solids divided by weight of milk taken, multiplied by 100, represents percentage total solids.

Method I. Remove about one-half pound butter from the different parts of the churn or tub with a butter trier, and put this into wide-mouthed bottle or Erlenmeyer flask fitted with rubber stopper having a thermometer in the center of the stopper, and reaching down into the mass of butter. Heat bottle in hot water until thermometer reaches 40 deg. C. or 104 deg. F. If this temperature is not exceeded, there is very little danger of the butter-fat spreading rapidly from the curd. Shake vigorously.

Method II. Another very satisfactory method of preparing butter for sampling is to put butter as it comes from churn or tub into Mason jar, beaker, glass tumbler, or wide-mouthed bottle, any of which may be covered tightly to prevent evaporation. Allow these to stand in warm room or in warm water until the butter is soft enough so that it may be stirred thoroughly with table knife, spatula, or a mechanical stirrer. At temperature of about 75 deg. to 80 deg. F. butter stirs into a waxy form from which water or casein will not separate. In this form, it is put into boat or flask to be weighed.

 (1) If sampling method I is used, measure (about) 1 gram into weighed butter boat. Weigh quickly and insert boat into flask. If sampling method II is used, put about 1 gram of the butter sample into weighed boat, weigh quickly, and insert into extraction flask.

 (2) Remove flask from holder and add to extraction flask 9 cubic centimeters hot water from aluminum dish placed on fat plate. Mark 10-gram pipette up to 9 cubic centimeter and use this for measuring hot water. Shake vigorously so as to mix butter thoroughly with water.

 (3) Before replacing flask into holder, add 1¹⁄₂. cubic centimeters C. P. ammonia and shake thoroughly, making sure that butter is thoroughly mixed with ammonia.

 (4) Add 10 cubic centimeters of 95 per cent alcohol. Insert cork. Replace flask into flash holder. Shake flask thoroughly with cork inserted. Use best quality corks only.

 (5) Cool flask by running cold water over lower end of extraction flask, if flask is very hot. This is not ordinarily necessary.

 (6) Add 25 cubic centimeters ethyl ether. Insert corks, shake vigorously until all butter is dissolved out of boat. Then add 25 cubic centimeters petroleum ether and repeat operation.

 (7) Centrifuge flasks, turning handle thirty turns after centrifuge has reached a speed of about 600 revolutions a minute.

 (8) Pour off extractions into proper weighed 3¹⁄₂ inch aluminum dishes. Repeat above extraction, adding successively 5 cubic centimeters of 95 per cent alcohol, then 25 cubic centimeters of each ether. Excepting for very accurate work, a third extraction is not necessary. The second extraction will remove all but .10 to .15 per cent of the butter-fat. For factory control work this would be a good margin of safety.

 (9) Evaporate off ether at 135 deg. C. on “fat plate,” and when all of ether is off, dry fat in fat oven held at 135 deg. C. for five minutes after the vacuum has reached at least 22 inches.

(10) Cool, weigh, and calculate percentage butter-fat as in regular fat test.

If sampling method I is used, keep butter at 140 deg. F. and mix thoroughly and while well mixed, weigh 1 gram into the solids dish as quickly as possible to prevent evaporation. If second method of sampling is used, weigh 1 gram of butter into the solids dish. Heat on hot plate at 180 deg. C. until foaming ceases, and then place in vacuum oven held at 100 deg. C. for seven minutes. Cool, weigh and calculate percentage solids; 100 less this figure represents percentage moisture.

 (1) Use the 10 gram pipettes for measuring out 10 grams of milk into cleaned but not necessarily dried Mojonnier extraction flask. Use only 10 gram pipettes furnished with tester and do not use 10 cubic centimeter pipettes. The pipette is graduated to deliver 10 grams of milk, after allowing all milk to run out and letting it drain for fifteen seconds longer, then blowing gently to remove last drop. The pipette must be perfectly clean and dry before being used. Wash frequently with sulfuric acid, water, alcohol, and ether to insure having a clean pipette.

 (2) Make extractions exactly as in test for butter-fat in condensed milk, excepting that no water need be added, and in second extraction only 15 cubic centimeters of each ether need be used.

 (3) Percentage butter-fat is obtained by multiplying the weight of the extracted butter-fat by 10.

 (4) If any of these products have soured badly, double the quantity of ammonia in the regular extraction and shake until all particles are dissolved.

Determining total solids as in evaporated milk, excepting that a 2-gram sample is weighed out, and no water need be added to spread the milk over the bottom of the dish.

Mix the sample thoroughly, making sure that it is sufficiently pulverized, and representative of the entire lot to be tested. In the case of milk chocolate, pulverize the sample very thoroughly, in a close grained mortar. Transfer the pulverized sample promptly to a sealed jar. Mix before removing portions for testing.

 (1) Weigh out rapidly, to prevent absorption of moisture from the air, about 1 gram of milk powder into butter boat. In case of malted milk, milk chocolate and cocoa, weigh out a 0.5 gram sample.

 (2) Add 8.5 cubic centimeters of hot water to flask. Insert cork. Heat flask in water boat, and shake thoroughly until the sample is well mixed.

 (3) Add 1.5 cubic centimeters (one charge) ammonia, and shake thoroughly.

 (4) Add 10 cubic centimeters of 95 per cent alcohol. Shake thoroughly. Cool the flask, if necessary.

 (5) Continue the extraction exactly as directed under the butter-fat determination, paragraphs 4, 5, 6, and 7, inclusive.

Use .3000 gram sample. Add 2 cubic centimeters distilled water to the sample in this dish. Otherwise continue the determination exactly as directed under total solids determination in cheese.

Mix sample thoroughly in the container. If the cream has been homogenized, it can be weighed with the weighing pipettes as described under 5, page 230 of these directions. If the cream is churned or lumpy it has to be heated until the fat is all just barely melted, and the entire mixture is uniform. Cream is a product that is subject to many variations in composition, degree of acidity, and physical condition. For these reasons, the operator needs to exercise the best judgment possible. The method of operation may require, at times, slight modification, depending on the condition of the sample.

 (1) For cream testing under 15 per cent butter-fat, take about a 2 gram sample, using 2-gram pipette. For cream testing over 15 per cent butter-fat take a 1-gram sample. If practicable, weigh out of pipette as described under 5, page 230. Otherwise weigh the sample in the butter boat, or directly into the extraction flasks, which were previously weighed.

 (2) Remove flask from the holder and add enough water to make a total of 10 cubic centimeters. Insert cork and mix thoroughly.

 (3) Before replacing flask in holder, add 1.5 cubic centimeters (one charge) of ammonia. If the cream is sour add 3 cubic centimeters of ammonia. This is very important.

 (4) From this point to the end of the test, continue as stated on page 231, beginning at paragraph 2 to paragraph 16, inclusive. At the end of the second extraction it may be necessary to add quite a little more alcohol, in order to bring the dividing line up to the required height.

Use a 1.0 gram sample. Add 1 cubic centimeter distilled water to the sample in the dish. Otherwise proceed exactly as directed in sections 3 to 7 of page 233.

 (1) Before the reagents are put into the cans, be sure that the cans are thoroughly cleaned by washing all parts, first with warm water, then alcohol and then ether. Every third or fourth time cans are filled, empty out last portion of reagents, and use for cleaning purposes.

 (2) The bottoms of all dishes should be kept as flat as possible. Any bulging may be worked out by resting dishes upon marble plate in front of balance, rubbing entire bottom surface with thumbs. Operator should observe this every time dishes are cleaned. This is very important.

 (3) The calcium chloride in the coolers should be changed every three or four weeks. The same calcium chloride may be used over and over by drying the used calcium chloride in tin dishes placed upon hot plate held at 135 deg. C. for at least five hours.

 (4) The bottles should be whirled in the centrifuge until the ether extraction is perfectly clear. About thirty turns at a normal speed are to be recommended. For sweetened condensed milk this time must be doubled.

 (5) Be sure to keep extraction flasks perfectly clean. Wash often with sulfuric acid and washing powder, if necessary. If particles cling to the sides put in small shot, washing powder and hot water, and shake thoroughly.

 (6) Keep temperature regulated as nearly to standard temperature as possible.

 (7) Never pour off extraction into a hot dish. Remove dish from plate before second extraction is run into dish.

 (8) Be careful to pour off ether into dishes slowly at first and gradually increase stream until full stream is running.

 (9) In using weighing pipettes, make sure that neck of flask is free from water when pipette is inserted.

(10) Always use clean and dried pipettes.

(11) If the samples for solids have to stand for any length of time, add the water just as soon as they are measured out, otherwise there is a tendency to dry and a good mixture with water cannot be obtained. Keep dishes upon marble plate beside the balance, and not on hot plate support.

(12) Redistill ethyl ether and petroleum ether, unless they are known to be pure. This is unnecessary if these are bought from a reliable firm.

(13) Make sure that water is always running through cooling plate. Watch pipe back of cooler. If tester is located in cold room in winter, add a gallon of denatured alcohol to tank to prevent freezing.

(14) Always aim to weigh empty dishes just before you are ready to use them. It is not advisable to weigh them a long time before they are used.

(15) It is fundamentally important to see that weights are read and posted rightly. Operator should-keep his weights in systematic order upon balance pan. When a reading is taken, it should be checked at least three times. Learn to make weighing absolutely correct. One figure misread may cost a month’s salary.

(16) Every operator should from time to time have a sample checked by a thoroughly reliable laboratory. Mojonnier Bros. Company, Chicago, Illinois, maintain such a laboratory exclusively for this purpose. Charges very moderate.

If results on fat are high as compared with check results, the cause may be one of the following:

(a) Not keeping bottoms of dishes flat.

(b) Improper shaking and centrifuging shown by non-fatty residue in dish.

(c) Improper reagents (if in doubt run test upon reagents substituting water for milk).

(d) Temperature in fat oven too low.

(e) Dirt has gotten into dish after ether was poured into it.

(f) Improper reading or posting of weights. Weights have lost weight from use.

If results on fat are low as compared with check results, the cause may be one of the following:

(a) Leaky corks. Use best corks obtainable.

(b) Insufficient shaking.

(c) Adding too much water.

(d) Having dividing line too low, so that too much ether is left behind. If such is the case, add more alcohol to bring line to the proper height, before pouring off, or make a third extraction.

(e) Too high temperature in vacuum oven.

(f) Not having water running through cooler. Tank must be kept filled.

(g) Improper reading or posting of weights.

If results on total solids are too high, as compared to check results the cause may be one of the following:

(1) Bottoms of dishes are not kept flat.

(2) Evaporation upon solids plate has not been carried far enough. Be sure to manipulate dish so that vigorous boiling takes place upon the entire surface of the bottom of the dish. Do not remove dish until all visible moisture is off or until first trace of brown coloration appears.

(3) Improper reading or recording of weights. Weights have lost weight from use.

(4) Dirt has fallen into dish after sample has been weighed into it.

(5) Temperature in vacuum oven is too low.

(6) Vacuum is not up to standard.

If results on total solids are too low, the cause may be one of the following:

(1) Sample is browned too much upon outside hot plate.

(2) Temperature in vacuum oven is above 105 deg. C.

(3) Milk spattered from dish. This will not happen if temperature is kept at 180 deg. C.

(4) Improper reading or recording of weights.

(5) Water is not running through cooler.

First operation: When starting to freeze a new batch, see that over-run cup is adjusted as described.

Second operation: Draw exactly five gallons of cream into the hopper above freezers when using a ten-gallon freezer. (If larger freezers are used, draw a volume into the hopper equal to one-half rated capacity of freezer.) It is well to graduate and mark very plainly the one-half capacity upon the hopper of the freezer.

Third operation: Run mix into the freezers as usual, filling all four freezers, while the freezers are running.

Fourth operation: Turn on the brine and continue whipping.

Fifth operation: The brine temperature and the brine pressure should be such that about 100 per cent over-run can be obtained with the brine turned off, and by turning on the brine again, will result in the over-run going down too quickly. If turning on the brine after whipping does not reduce the over-run, it is an indication of poor brine temperature. In that case, shutting down the machine for a short time is advisable, in order to get the brine temperature down to a point where freezing may be done efficiently, and the yield or over-run kept under proper control.

It is well to regulate the proper pressure according to the brine temperature until the desirable over-run is obtained. There is a fixed relation between these two factors, and by using the over-run test as a guide, it is possible to adjust the pressure to the temperature necessary to obtain the best over-run.

Brine valves on each freezer should be kept in good condition so that when they are turned off, there is no flow of brine through the freezer. A leaky valve may cause the over-run to refuse to go up, due to the low temperature of the batch, thus preventing proper whipping. Whip with the brine on until the ice-cream is quite stiff. At this point, take test for over-run. If a satisfactory over-run is procured, turn on brine and draw off batch. If a satisfactory over-run has not yet been obtained, turn on the brine and continue whipping until by repeated test, the proper over-run is obtained. After the freezer is emptied, this operation is repeated in the same way.

Many operators make it a point to draw off ice-cream when over-run shows between 90 and 100. Ice-cream with over-run of more than 110 per cent is usually not a satisfactory commercial product.

Sixth: Record under the proper freezer number on the freezer-room blank, the final over-run test indicated when the cream is drawn. Do not record any but the final result. This will form a valuable check on the volume of ice-cream as recorded in the hardening-room. It is possible in this way for the manager of the plant to obtain an accurate idea of how careful the over-run has been controlled.

Operating under the second method, or when a girl makes the over-run tests.

Under this method, the helper in the freezer-room should not draw off the ice-cream until it has been carefully tested and controlled. One girl can test and control the over-run of ice-cream from six freezers with one over-run tester, having three freezers on each side. She can keep close watch of the frozen cream through the peep hole in top of the freezer. As soon as the cream seems to be of the proper consistency, a test of the over-run should be made.

Principal causes of variation in over-run: