The _packing material_ may be either hay, straw, paper, wool, mineral
wool, excelsior, ground cork, Southern moss, sawdust, or any other
non-conducting material that is adapted to filling the space between the
kettle and the box. If hay is used, choose soft hay. Wool is, perhaps,
the best heat retainer of those mentioned, and it is easy and pleasant
to handle. Clean, soft wool may be purchased at woollen mills and
elsewhere. It should cost about thirty-five cents a pound, but as it is
very light it requires much less, by weight, than of some other cheaper
materials. Mineral wool can be purchased at large hardware stores. It
costs about five cents a pound, but about five times as many pounds are
required as an equivalent for wool. Cheap cotton batting can be obtained
at dry-goods stores; ground cork from large grocers. This is used by
them as packing for grapes or other fancy fruits. Sawdust, obtainable at
sawmills, and perhaps elsewhere, must be well dried before using.
Excelsior is used by many kinds of merchants, and can be bought for
about two cents a pound. Hay is plentiful in country places and can also
be purchased at feed-stores in the cities. Southern moss, easily
procurable in the Southern States, can be found at many upholsterers’ in
the North as well. Newspapers and hair, such as is used by plasterers,
are available in city and country.
_The utensils._ Perhaps the best _shape_ for the cooking utensil, that
is, one which will have the least possible radiating surface, is a pail
about the depth of its own diameter. The sides should be straight and
perpendicular to the bottom. The cover should fit securely into place.
If a smaller utensil is to be used inside the large one, which is often
a great convenience, it must not be so high that the cover of the larger
pail will not go on. A “pudding pan” may be used for the inside utensil,
resting on the rim of the pail; but care must be taken, with this
arrangement, that a cover is secured that will fit the pan closely.
To select the _material_ best adapted for cooker utensils one must
consider its wearing quality, its heat-absorbing power, to some extent,
and also the action upon it of the water, acids, salts, etc., which are
found in the foods. For instance, iron utensils, as well as most tinware
that has been used for any length of time, will rust with the long
subjection to heat and moisture; acids will make a disagreeable taste
with iron or old tin utensils; while acids in such long contact, with
even new tin might also form poisonous tin salts in sufficient quantity
to be decidedly injurious. Earthenware would seem ideal except that it
is likely to break when over the flame. It is desirable that the covers
be of the same material as the utensil, or of some other rust-proof
material. It will pay to get the best, when buying these kettles, for
they will last well, with reasonable care, and a poor utensil will soon
be of no use whatever. Well-enameled iron, except for its weight, is
good; also the best quality of agate ware, ordinary aluminum, or,
perhaps best of all, for very large utensils at least, cast aluminum.
Aluminum is expensive, but its light weight, excellently fitting parts,
and lasting qualities commend it above other materials, and it will be
found to pay in the end.
The _size_ of the pails will depend to some extent upon the number of
people to be served, although there is a minimum size, below which there
is not a sufficient bulk of food to cook well. Under the heading
“Practical Suggestions on the Use of the Fireless Cooker,” this matter
of quantity is more fully discussed. For a family of five or six persons
a six-quart pail with a pan to fit inside of it has been found
satisfactory. It will be convenient to have also a larger pail for large
pieces of meat, such as hams.
_Method of packing the box._ This will vary somewhat with the different
insulating materials used. These may be classified as:
Those into which the cooking utensil may be set without any intervening
covering, among which are hay, excelsior, and paper.
Those requiring a covering material to keep them in place and to protect
them from contact with the utensil, among which are wool, mineral wool,
cork, sawdust, and cotton.
[Illustration: Figure No. 1.