Such sirups as are used in canning and preserving are made with varying
proportions of water and sugar. When the proportion of sugar is large
and that of the water small the sirup is said to be heavy. When the
water predominates the sirup is light.
There are several methods of measuring the proportion of sugar in a
sirup. The most scientific and accurate is with the sirup gauge. Careful
measurement or weighing is, however, quite satisfactory for all ordinary
work if the sirup need not be boiled a long time. In boiling the water
evaporates and the sirup grows thicker and richer. The amount of
evaporation depends upon the surface exposed and the pressure of the
atmosphere. For example, if a large quantity of sirup is boiled in a
deep kettle the evaporation will not be rapid. If the same quantity of
sirup were boiled the same length of time in a broad, shallow kettle the
water would evaporate more rapidly and the sirup would be thicker and
heavier. If a given quantity of sirup were boiled the same length of
time in a high altitude, Colorado for example, and at the sea level, it
would be found that the sirup boiled at the sea level would be thicker
and less in volume than that boiled in Colorado. From this it will be
seen that it is difficult to say what proportion of sugar a sirup will
contain after it has been boiling ten or more minutes. Of course by the
use of the sirup gauge the proportion of sugar in a sirup may be
ascertained at any stage of the boiling. After all, however, it is
possible to measure sugar and water so that you can know the percentage
of sugar when the sirup begins to boil. The following statement gives
the percentage of sugar at the time when the sirup has been boiling one
minute and also what kind of sirup is suitable for the various kinds of
fruit:
One pint sugar and 1 gill of water gives sirup of 40°
density: Use for preserved strawberries and cherries.
One pint sugar and one-half pint water gives sirup of 32°
density.
One pint sugar and 3 gills water gives sirup of 28°
density: Use either this or the preceding for preserved
peaches, plums, quinces, currants, etc.
One pint sugar and 1 pint water gives sirup of 24° density:
Use for canned acid fruits.
One pint sugar and 1½ pints water gives sirup of 17°
density.
One pint sugar and 2 pints water gives sirup of 14°
density: Use either of these two light sirups for canned
pears, peaches, sweet plums, and cherries, raspberries,
blueberries, and blackberries.
The lightest sirups may be used for filling up the jars after they are
taken from the oven or boiler. The process of making a sirup is very
simple, but there are a few points that must be observed if sirup and
fruit are to be perfect. Put the sugar and water in the saucepan and
stir on the stove until all the sugar is dissolved. Heat slowly to the
boiling point and boil gently without stirring. The length of time that
the sirup should boil will depend upon how rich it is to be. All sirups
are better for boiling from ten to thirty minutes. If rich sirups are
boiled hard, jarred, or stirred they are apt to crystallize. The sirup
may be made a day or two in advance of canning time. The light sirups
will not keep long unless sealed, but the heavy sirups keep well if
covered well.