To a casual observer mortar is mud, but to a builder who understands the
chemistry of mortar it is a compound of water, lime and sand, and when
properly prepared forms an indestructible cement. Fresh slacked lime,
when brought in contact with clean, sharp sand, adheres strongly to the
surface of each grain, and forms the silicate of lime.
At the same time the drying mortar absorbs carbonic acid from the
atmosphere, forming with it lime-stone, which in time becomes a rock in
solidity. Now, all mortar is good or bad in proportion to the purity of
the ingredients and their relative affinity for each other. The adhesive
properties of mortar are nullified by loam or clay in sand, or the stale
condition of lime used.
Loam mortar adheres freely to the surface of walls or ceilings. So does
mud if thrown against an upright surface; but water dissolves it. It
dries quickly, but does not harden with age. The foundation of many
frame, and the entire walls of many brick houses are built with poor
mortar, when the materials for good could be had at the same price.
Water, lime, sand and hair are the ingredients for plasterers’ mortar
in about the following proportions: One bushel unslacked lime and four
bushels sharp sand; (to this add twenty-four pounds of dry hair for every
one hundred yards, when used for “scratch” or first coat,) and water
sufficient to make it of proper consistency. After being properly mixed,
the mortar should stand from three to ten days before using. However,
the time it should stand depends upon the susceptibility of the lime to
slack. Some lime requires a month, while good lime slacks immediately.
Age improves mortar, provided it is kept wet, and makes it work easier
under the workman’s trowel. As it is the keys formed by pressing the
mortar against the lathing on the ceiling that holds it to its place,
there should be a relative width of lath and key space to insure strength
sufficient to prevent its falling. Ignorance of this, and poor mortar,
is the cause of falling ceilings. Lath one inch wide, 7/16 inches thick,
placed 7/16 inches apart will insure good strong work.
The second coat needs but a very small quantity of hair. Fifty bushels
sand, and twelve and one-half bushels unslacked lime, will make mortar
enough to cover one hundred square yards. If mortar freezes before it is
dry it loses its cementing properties and becomes in common phase rotten,
but if the sand used is clean, and it remains frozen without thawing
until it is dry, it is not injured. The best way to treat a house in
which the plastering is not dry, and cannot be kept from freezing before
it dries, is to throw the house open, and let it freeze for eight or ten
days, or until the plastering freezes dry.
Cisterns should be plastered inside with mortar made of equal parts of
hydraulic lime and clean sand. For brick work above foundations use one
part unslacked lime to four parts sand.
* * * * *
“THE INDEPENDENT,” 251 BROADWAY, NEW YORK, October 28th, 1889.
Gentlemen:—The shingles from your respected concern used on my
new house look splendidly, and give entire satisfaction. They
are far better than any metal shingles I have previously used
on other buildings, which I have had torn off and thrown away
as worthless. At times we were flooded by the water under their
(want of) protection, and we could not stop the leaks. Noah in
the ark I am sure was, fortunately, not troubled with leaks
such as we endured for years; if he had been all would have
been drowned. Now, under your protection, we are all right and
still alive.
Faithfully,
HENRY C. BOWEN,
CHANDLER.