4: Testing the egg.]
[Illustration: FIG. 5: four eggs.]
21. If nothing has been done to preserve eggs, the simple test for
freshness illustrated in Fig. 3, which consists in placing the eggs in a
glass containing water, will be found effective. A perfectly fresh egg
will sink when it is put into the water, but if the egg is 3 weeks old
the broad end will rise slightly from the bottom of the glass. An egg
that is 3 months old will sink into water until only a slight portion of
the shell remains exposed; whereas, if the egg is older or stale, it
will rise in the water until nearly half of it is exposed. 22. The
test known as candling, which is usually applied to eggs before they are
put on the market, can also be practiced by the housewife in the home.
This method of determining the freshness of eggs consists in placing a
piece of cardboard containing a hole a little smaller than an egg
between the eye and a light, which may be from a lamp, a gas jet, or an
electric light, and holding the egg in front of the light in the manner
shown in Fig. 4. The rays of light passing through the egg show the
condition of the egg, the size of its air space, and the growth of mold
or the spoiling of the egg by any ordinary means.
[Illustration: FIG. 6 (_a_) (_b_)]
In Fig. 5 is shown how an egg at various stages of freshness appears
when candled. When an egg is fresh, it will appear as in (_a_); that is,
the yolk will be barely distinguishable from the white except as a
slightly darker area in the center of the egg, and the entire egg will
appear clear and bright and free from spots.
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