Do not use very fine sand. If there is a large quantity of fine sand
handy, obtain a coarse sand and mix the two sands together in equal
parts; this mixture is as good as coarse sand alone.
Sometimes fine sand _must_ be used, because no other can be obtained;
but in such an event an additional amount of cement must be
used—sometimes as much as double the amount ordinarily required. For
example, in such a case, instead of using a concrete 1 part cement, 2
parts sand, and 4 parts stone, use a concrete 1 part cement, I part
sand, and 2 parts stone.
Besides being coarse, the sand should be clean, _i. e._, free from
vegetable matter. “But,” you say, “how shall I tell whether the sand is
what you call clean?”
The presence of dirt in the sand is easily ascertained by rubbing a
little in the palm of the hand. If a little is emptied into a pail of
water, the presence of dirt will be shown by the discoloration of the
water. This can be discovered also by filling a fruit jar to the depth
of 4 inches with sand and then adding water until it is within an inch
of the top. After the jar has been well shaken, the contents should
be allowed to settle for a couple of hours. The sand will sink to the
bottom, but the mud, which can be easily recognized by its color, will
form a distinct layer on top of the sand, and above both will be a
clear depth of water. If the layer of mud is more than one-half inch in
thickness, the sand should not be used unless it is first washed.
Having discovered that the sand you contemplate using is not clean, and
provided you cannot readily obtain any that _is_ clean, you may use
what you have, provided you wash it in the following manner:—
Build a loose board platform from 10 to 15 feet long, with one end a
foot higher than the other. On the lower end and on the sides, nail a
board 2 by 6 inches on edge, to hold the sand. Spread the sand over
this platform in a layer three or four inches thick, and wash it with
a hose. The washing should be started at the high end, and the water
allowed to run through the sand and over the 2 by 6-inch piece at the
bottom. A _small_ quantity of clay or loam does not injure the sand,
but any amount over 5 per cent. does.