Almost any material which will hold the concrete in place will do for a
Form. Concrete foundations for farm buildings require shallow trenches,
and usually the earth walls are firm enough to act as a Form.
Molds of wet sand are used for ornamental work. Frequently colored
sands are used for this purpose, providing both the finished surface
and color to the concrete ornament.
Cast, wrought or galvanized iron is used, where an extremely smooth
finish is desired, without further treatment upon the removal of the
Forms. Forms made of iron are more easily cleaned, and can be used a
greater number of times than those of wood. Rusty iron, however, should
not be used.
By far the greatest number of Forms are made of wood, owing to the fact
that lumber in small quantities can always be obtained.