As we have seen in the case of the insulating pail, the principle
involved in cooking by retained heat may be reversed, and the heat may,
by similar means, be excluded from foods which are to be kept cold.
Ice-boxes and refrigerators are made with this end in view. They are
constructed with heavy walls, usually, if not always, with an
interlining of some non-conducting material, to exclude the heat of the
atmosphere. Where such an article is needed permanently, or for large
quantities of food, the various refrigerators on the market are better
adapted to the purpose than a home-made box. But, in cases of temporary
necessity or to supplement a refrigerator, the home-made refrigerating
box will doubtless find a use. Ingenuity will suggest variations in the
manner of applying the principle of insulation to keeping foods cold,
but by way of suggestion two forms of refrigerating boxes are described
below.
[Illustration: Refrigerating box packed with three crocks.]
Take three or more stoneware crocks with well-fitting covers of the
same material. The size of the crocks must be determined by the quantity
of food to be kept. Good results in the way of temperatures have been
obtained with those holding a half gallon, but the amount of food
accommodated in them is, of course, small.
Proceed exactly as for packing a cooker, except that the crocks must be
set in place so that all of them touch the central one, which is to be
filled with ice.
Although any insulating material suitable for cookers will answer for a
refrigerating box, sawdust will be found the easiest to handle, for the
reason that its fine particles will more readily fill the acute angles
between the crocks, which must be carefully packed or the insulation is
not complete. It will be best to make one narrow cushion that may remain
in place over the central crock, except when the ice is to be renewed,
and two others, each of which can be removed singly when the crock under
it is to be opened. Put the food into dishes or pails that can be
removed with it and washed. This will obviate the necessity for taking
out the crocks frequently and will mean a considerable saving of ice. In
lieu of one solid piece of ice, broken pieces will be found to answer
excellently. Fill the ice-crock as full as possible, and do not open it
until it needs refilling. A little observation of your own individual
box will be necessary to tell you just how long your crock of ice will
last. It will probably be safe, in any case, to leave it two full days
after filling it before opening it. If no foods that have not been
reasonably cooled are put into the refrigerating box it is possible that
the ice may last three or four days.
Aside from the efficiency of the insulation, the consumption of ice will
depend largely upon the amount and temperature of the food in the other
crocks and the frequency with which they are opened to the warm outside
air; therefore chose as cool a place as possible for the box to stand,
and open it only when necessary. Try to think of all the articles you
want from it before taking off the cushion. Better results in the way of
temperature can be obtained with these boxes than with many commercial
refrigerators, although the skill and care in using either will be a
large factor in the economy of ice. When it is necessary to open the
box, let it be for as brief a time as possible, as every moment that it
is open means an increase of temperature and, consequently, a loss of
ice.
Another variety of refrigerating box may be made by thoroughly
insulating a tin pail partly filled with ice, or a bread box, containing
a crock for ice. Allow the same amount of insulation as that called for
with the various packing materials used for hay-boxes or cookers, and
pack them similarly. It will not often be necessary to remove the inner
box if care is taken in handling the dishes of food; but when it is to
be scalded, take it out, wash it well, boil or scald it with soda and
water, and cool it again before replacing it in the packing.