While ice, for many years, has been an indispensable article in the good conduct of households, only recently has its efficient utilization received serious attention. Like the electric current and gas its benefits must be made apparent through suitable appliances.
The old "ice box" is being definitely superseded by the scientifically designed and constructed ice-cooled refrigerator in which are maintained the temperatures designated by bacteriologists and biochemists as necessary for the proper preservation in the home of milk, fresh meats, fruits, vegetables and the like. For example, the portion of the refrigerator receiving the current of air just off the ice is less than 450 F. even when atmospheric temperatures are continuously at 900 F. and the contiguous sections are well below 500 F. Particular attention has been paid to obtaining 450 F. or less for milk and delicate foods, since, more and more, we learn that 45o F. is, for them, the crucial temperature line. For most vegetables and fruits, however, temperatures from 50o F. to 55o F. are adequate for household needs.
The modern refrigerator for ice has abandoned the so called "dead air space" for insulation and has substituted from one to three inches of pure corkboard or its equivalent. It has properly adjusted openings for air circulation and a "baffle" between the ice compartment and the food compartment which guides the direction of the air movement.
There should be available a section of the wall of every refrigerator sold that the purchaser may see for herself (1) the thickness and kind of insulator, (2) the entire absence of so called "dead air spaces," (3) the presence, location and kind of waterproofing compound used to protect the insulation from moisture, (4) the reasonable use of paper to protect the surface of the insulator but not to be depended upon for insulation.
The primary requirements in choosing insulators for household refrigerators are (1) high resistance to the passage of heat and (2) high resistance to the absorption of moisture such as is exhibited by pure corkboard. The heat resistance of balsam wool, dry-zero, and to a lesser degree insulite, celotex, nu-wood, weatherwood, and flaxlinum, has permitted these materials to function in refrigerator walls when properly waterproofed. The less the resistance to heat, the thicker the layer of insulator must be. Therefore, the purchaser should insist upon knowing the name of the insulator and the thickness of it.
1 Part of the following article has been adapted from Buying a Refrigerator (Household Refrigeration Bureau, National Association of Ice Industries, 1930), and the remainder has been prepared by Dr. Pennington for this publication.
Regardless of other qualities, insulators used in refrigerators should be strong enough to stand up without support. This requirement places granulated cork, mineral wood, asbestos wool and similar substances in the category of the unreliable insulators for household refrigerators. Refrigerators containing them lose their efficiency too rapidly to be either reliable or economical. Balsam wool, dry-zero and flaxlinum are manufactured in panel form and, if properly protected against moisture absorption, the slabs wear well. In flexible blanket form they are, with our present methods of building, much less reliable.
Microscopic air spaces such as nature puts into corkboard are our most efficient insulators. But man cannot build such tiny, tight spaces into walls and what man terms "dead air spaces" soon become almost valueless in a household refrigerator. For example, a refrigerator with air space and paper in its walls melted 28 pounds of ice per day and gave a temperature in the top of the food compartment of 62.8° F. A similar refrigerator with two inches of good insulation under exactly the same conditions melted 25 pounds of ice per day and maintained a temperature of 51.9o F. on the top shelf.
Too often the "bargains" advertised at low prices, or the sales of refrigerators put on to attract customers, are based on air and paper cabinets without any real insulation. The salesmen have been known to justify their statements by quotations from government bulletins in which were set forth laboratory experiments but they were not applicable to refrigerators of which fact the salesmen may have been ignorant.
Of course, the initial cost of air and paper is much less than the cost of a good insulator. But such refrigerators, in spite of good icing, do not protect foods. They soon acquire wet walls, melt ice extravagantly and increase running costs beyond all reason.
Some refrigerator walls appear thick because some manufacturers have alternated air spaces with layers of insulation. Or, they have left a space next to the inside lining. Such walls will not wear well because they are not air tight and so water will condense in them even when both inside lining and outside sheathing are steel. When an insulator is wet - or even damp - heat can go through it easily. Protecting against water absorption is a difficult part of refrigerator construction.
Atmospheric air is sure to get into the walls and it always carries more or less moisture which condenses when it penetrates to a cold part of the wall, especially the part near the inside lining since that is coldest. Therefore, a coating of some good water resisting compound, such as odorless asphalt, should be applied to all surfaces. If this asphalt binds the self-supporting insulator firmly to the interior lining on the one side and to the outer sheathing on the other, the insulator will be kept dry and stay in place for many years. Such construction, also, is an efficient way of eliminating air spaces. Because of the difficulty in applying hot asphalt to such surfaces, heavy paper impregnated with odorless asphalt is often used to cover or wrap the slab of insulation.
The lining of a refrigerator should be porcelain or vitreous porcelain on steel if the purchaser can afford it. At lower cost one can now obtain good white enamel-on-steel linings which wear well if well made.
Whether of porcelain or enamel, the inside lining should extend unbroken around the ends and back of the refrigerator and the top and bottom should be put on with well-made locked seams. The old type of L lining which necessitated separate fitted pieces for the lining of the ice compartment is undesirable and is rapidly being replaced by linings of the "one piece" type. The enamel metal linings have seams in them. It is the aim of the conscientious manufacturer to make these seams as air tight as possible and they are constantly improving their work.
The vitreous porcelain is truly in one piece and so is better able to protect the walls against moisture. The old-fashioned L type of porcelain lining is much less desirable than the continuous type now much used.
All corners should be rounded to facilitate cleaning. Formerly only porcelain could have rounded corners but now enameled linings have them.
The purchaser is especially interested in the openings to carry the air to and from the ice; in the construction of the baffle because of its influence on air circulation; and in the amount of food space. When buying, be sure that the refrigerator is up to date in these items.
Unless there is abundant and continuous circulation of air, the food will not be well kept. To obtain good air circulation we must have (1) the surface of the ice unobstructed, (2) a large opening for the air to escape from the ice compartment, (3) a guide to direct the cold air all the way down to the floor of the refrigerator and all the way up above the top shelf.
Since we must have an open, uncovered ice surface to most rapidly and efficiently absorb heat and food odors, it is obvious that appliances in which the ice floats in water or is encased in metal over which the passing air is to be cooled decrease refrigerating efficiency.
Almost without exception those refrigerators so designed and constructed that they cool and deliver drinking water through a faucet have food compartment temperatures which are too high for the adequate protection of food. It is better to put drinking water into bottles, lightly stoppered, and set them into the well-iced refrigerator in the milk or food compartment.
In the middle of the floor of the ice compartment in the side icer refrigerator there should be an opening having an area at least one quarter of the total area. In refrigerators having from five to eight cubic feet of food space this cold air outlet is usually from six to eight inches wide and from 10 to 12 inches long. It is well, when selecting a refrigerator, to remove the ice rack and measure this opening because if it is too small, the refrigerator will not function properly. There should be a space between the ice rack and the walls of the ice compartment that the cold air may fall easily to the floor of the compartment and so through the hole. The surface of the ice rack should stand at least one and one half inches above the bottom of the ice compartment. Otherwise, the flow of air is cramped and, also, there is likely to be sweating of the surface of the metal ceiling of the milk compartment.
Thus will the air, cooled by passing over the surface of the ice which is never more than 32° F., find a ready exit into the space where the food is kept.
The next item to be sure of is that the air traverses completely the body of the refrigerator and cools every portion of it. A simple and efficient method of guiding the cold air is to extend upward and downward the partition which separates the ice compartment from the food compartment, and to put within this partition some insulator so that it is less cold than all metal would be.
Such an extension we call a "baffle" and for the best results it should reach to within five inches of the floor and six inches from the top of the refrigerator in cabinets of larger sizes. Then the air falling through the large cold air down drop must continue to fall until it sweeps the floor whereon stand the milk bottles and containers holding the most perishable foods. Then it rises quite evenly, because it is picking up heat as it goes, until it passes over the top of the baffle where there is plenty of space for it to travel easily, and so over the surface of the ice again. The baffle must be solid - that is, free from openings directly into the food compartment.
If such exist, the circulation of air above the level of the ice will be very sluggish and, consequently, the upper part of the refrigerator will be warm. While this defect may not be felt when the refrigerator is full of ice, it will be when the ice level falls.
We can easily see that the better the insulation and the better the workmanship, the more space, provided the design of the interior is correct, will a given amount of ice cool. From this knowledge we can properly reason that a refrigerator having an unduly large proportion of its interior space devoted to ice - such, for example, as 45 to 50 per cent - is not so economical a refrigerator nor, all other things being equal, so good a purchase as the refrigerator of the same total interior capacity which is properly cooled with 30 to 40 per cent of that space devoted to ice. Given a total capacity of 10 cu.ft., in the one case the housewife would have 6.5 cu. ft. for food space while, with the unduly large ice chamber, she would have but 5 to 5.5 cu. ft. for food.
Recently the United States Bureau of Standards fixed the minimum sizes of the door openings and the depth of the ice compartments,1 when they are to accommodate 25, 50, 75, 100 and 150 pounds of ice, each quantity to be in a single piece and each to conform to the standard sizes for such weights.2 The most progressive and reliable refrigerator manufacturers have adopted the recommendations of the Bureau of Standards so that the purchaser, armed with the knowledge, can properly insist upon being provided with such a refrigerator. Equipped when she goes to buy, with a tape measure or a foot rule, she can for herself measure the height, depth and width of the interior and so find the total cubic capacity. Then removing the ice rack, she can measure the height, width and depth of the ice compartment and so determine the proportion which its space bears to the whole. Of course, she will measure the door opening3 to be sure it conforms to the Bureau of Standards requirements.
The standardized ice compartments have given the wide awake refrigerator manufacturer a chance to build systematized refrigerators where, with the same amount of space devoted to ice, better building and
1 Dept. of Commerce, Bureau of Standards, Division of Simplified Practice, Simplified Practice Recommendations R 109-29: Refrigerator Ice Compartments.
2 Dept. of Commerce, Bureau of Standards, Division of Simplified Practice, Simplified Practice Recommendations R 96-28: Ice Cake Sizes.
3 Door openings in clear:
25 lb. 8" by 12" 75 lb. 12" by 20" 150 lb. 12" by 24" 50 lb. 12" by 16" 100 lb. 12" by 23" better insulation will enable that ice to cool a greater and greater amount of food space, as well as give longer wear and a more pleasing appearance.
For example, when the walls of the properly-built refrigerator contain the equivalent of one inch of pure corkboard, 100 pounds of ice in a standard size ice compartment can refrigerate about five cu. ft. of food space. If the wall has the equivalent of one and one half inches of corkboard well installed, the 100 pounds of ice within the same ice compartment can cool from six to seven cu. ft. of food space. And when we have from two to three inches of pure corkboard insulation, the food space which 100 pounds of ice can cool is a minimum of eight cu. ft.
The foregoing illustration shows the application of the information obtained by scientists working on the principles of economical and efficient refrigerator construction, when the ice cut is constant. It applies in principle to the 75 and 50 pound cuts also.
Now let us see how the principle might apply if the purchaser had a definite idea in her mind of the amount of food space which her family required and wished to maintain the properly low temperatures necessary at a minimum expense for ice.
Should she need about five cu. ft. of refrigerated food space, she could obtain it in a cabinet in which the ice compartment is dimensioned to hold 100 pounds of ice. Then the ice compartment would occupy about 40 per cent of the total inside capacity. If, however, she selects a refrigerator having more insulation and better construction, she can have the five cu. ft. of space for food refrigerated with an ice compartment dimensioned for 75 pounds of ice. And with the very best of insulation and construction she will find that five cu. ft. of food space can be refrigerated satisfactorily by an ice compartment of 50 pounds' ice capacity as specified by the Bureau of Standards. The space required for 50 pounds of ice when added to the five feet of food space desired by the purchasing housewife gives a total interior volume of about 7.5 cu. ft. of which the ice occupies about 30 per cent of the total insulated space.
Let the thrifty housewife remember, also, that ice must melt to cool the ice compartment as well as the food compartment. But because no foodstuffs of any kind should ever be put into the ice compartment, there is no direct return for the ice unnecessarily melted to cool an ice compartment which is larger than it needs to be.
Chemists and bacteriologists working in their laboratories have ascertained that an average temperature not to exceed 450 F. in the milk compartment and not to exceed 500 F. in the food compartment is adequate for the protection of foods in the home. These temperatures have been broadcast far and wide so that the housewife is now familiar with them and demands that her refrigerator gives them.
The two general types of refrigerating systems are the compression and the absorption type. A large number of makes of compression-type machines are on the market. Most users are more interested in service, service cost, and machine cost than in refrigerants, kinds of drives, absorbents, or systems of refrigeration. Consideration by the purchaser of the following factors is important: (1) Standing of the manufacturer, (2) record of the machine, (3) noise, (4) length of life and cost of service and repairs, (5) efficiency, (6) insulation of the refrigerator, (7) air or water cooling, (8) servicing of the machine, (9) quality of local service, (10) comparison of refrigeration by machines and by ice.
In buying a machine it is best to depend upon a reliable manufacturer or agent. It is essential to have a high-grade cabinet as the preservation of food is of exceptional importance.
In selecting ice cabinets insulation is of great importance. Adequate insulation requires at least two inches of thickness of a good insulation material, adequately protected from moisture. The insulators should have high resistance to the passage of heat and high resistance to the absorption of moisture. For linings, porcelains or vitreous porcelains on steel are preferred. Less expensive linings are white enamel on steel linings. Openings should be sufficiently large to carry the air to and from the ice. The amount of food space and provision for air circulation is a consideration in buying. For good circulation: (1) The surface of the ice should be unobstructed. (2) There should be a large opening for the air to escape from the ice compartment. (3) There should be a guide to direct cold air. Refrigerators should have cold-air outlets sufficiently large for proper operation, and air should traverse all portions of the refrigerator.
Ackerman, W. T. Electric Household Refrigeration. Agricultural Experiment Station Bull. 244. Durham: University of New Hampshire, 1929. Pp. 23.
American Gas Association. Refrigeration with Gas - Why and How. New York: The Association, 1925. Pp. 61.
Includes list of mechanical and ice refrigerators.
Brookhurst, J., and Carlsson, V. "Keeping Food in the Home Refrigerator," Good Housekeeping, LXXXIII (July, 1926), 96.
Jordan, Ruth. Care and Use of the Home Refrigerator for Food Preservation. Extension Bull.. 147. Lafayette, Ind.: Purdue University, 1926. Pp. 8.
_______Factors in the Management of the Ice Cooled Refrigerator in the Home.
Agricultural Experiment Station Bull. 316. Lafayette, Ind.: Purdue University, 1927. Pp. 32.
Miller, G. E. "Electrical Refrigeration for the Home," Journal of Home Economics, XVIII (June, 1926), 303-7.
National Electric Light Association. Electric Refrigeration. More Power to the Home Series, Booklet 8. New York: The Association, n.d. Pp. 24.
Patty, Ralph L. Cost of Electricity for the Home Electric Refrigerator. Agricultural Experiment Station Bull. 241. Brookings: South Dakota State College of Agriculture, 1929. Pp. 16.
Pennington, M. E. Buying a Refrigerator (H.R.B. 12).1
_______The Care of the Home Refrigerator (H.R.B. 4).1
_______Cold Is the Absence of Heat (H.R.B. 8).1
_______How To Use a Good Refrigerator (H.R.B. 10).1
_______Where To Place Food in the Household Refrigerator (H.R.B. 3).1
Peyser, Ethel R. "The Gas System of Refrigeration," House and Garden, LI (February, 1927), 80, 168, 170.
Explanation of operation of gas-fired refrigerators of intermittent and continuous types. Includes cost of operation.
U.S. Bureau of Home Economics. Household Refrigeration. Home Economics Bibliography, No. 5. Washington: The Bureau, 1928. Pp. 24.
Whitton, M. O. The New Servant. Garden City, N.Y.: Doubleday, Page & Co., 1927. General information on electric refrigerators (pp. 213-26).
1 Published by the National Association of Ice Industries, Chicago, 111.