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Many people today will
tell you that the use of sidewalk chalk is a perfectly
acceptable material to rub on gravestones in order to
bring out the carving on hard to read stones. You may
find upon closer inspection that they are advocating
it's use on a stone that it's entire face has been
covered with newsprint, pellion or some other such
rubbing surface. They are not suggesting or recommending
the introduction of the chalk directly to the surface of
the stone.
However some will in fact
not only recommend this, but highly encourage it. It
this an acceptable method of highlighting the carving on
the stone? Saving Graves researched the question and put
it to experts to find out if it should be viewed as an
acceptable alternative method.
According to the Crayola
website, Molded chalk, such as Crayola Colored chalk, is
a softer chalk made of plaster of Paris, which is
defined as quick-setting gypsum plaster consisting of a
fine, white or gray powder, Calcium Sulfate
Hemihydrate (CaSO 4 ½H 2 O), which hardens when
moistened and allowed to dry. According to one
manufacturer, Calcium Sulfate Hemihydrate has
great applications in the manufacture of stucco, tablets
for ceilings, division panels, boards and sanitary
porcelain. In fact, it is most commonly called stucco
but not the same material as used on the outside of
buildings. A prime example of it's primary use would be
drywall sheeting.
gypsum materials expand
during setting,
primarily because the
dihydrate crystals push against each other
as they form
gypsum materials expand
during setting,
primarily because the
dihydrate crystals push against each other
as they form
gypsum materials expand
during setting,
primarily because the
dihydrate crystals push against each other
as they form
gypsum materials expand
during setting,
primarily because the
dihydrate crystals push against each other
as they form
gypsum materials expand
during setting,
primarily because the
dihydrate crystals push against each other
as they form
gypsum materials expand
during setting,
primarily because the
dihydrate crystals push against each other
as they form
gypsum materials expand
during setting,
primarily because the
dihydrate crystals push against each other
as they form.
Gypsum as a rule has a
tendency to expand as it sets. Therefore if the
material is left on the surface of the stone it is quite
possible that particles could work its way into the
stone and set causing the potential of damage to the
stone in several forms up to and including causing the
stone to break.
If it is introduced into
the stone by way of moisture, as that liquid evaporates
the gypsum will increase by double in strength and
hardness. In addition if a gypsum based element such as
chalk is left exposed to open air, once liquid is added
to it, the setting time is greatly shortened.
While sidewalk chalk is
somewhat softer than regular chalk we still do not
recommend it's use. In a test conducted by Saving Graves
it was proven that it regular chalk will actually
scratch a typical chalkboard. While being overall softer
in nature, the hardness of sidewalk chalk varies greatly
from manufacturer to manufacturer. Some of the lesser or
off brands that we tested were found to be as hard as
regular chalk.
To get an informed
opinion on the use of sidewalk chalk as a gravestone
rubbing took, we contacted Binney & Smith, the parent
company of Crayola located in Easton, Pennsylvania. We
ask them if they would as a manufacturer of sidewalk
chalk recommend it's use for gravestone rubbings. Saving
Graves received the following response from Crayola
concerning the use of sidewalk chalk:
"Crayola sidewalk chalk contains plaster of paris which
has a gritty texture. Plaster of paris is not considered
to be biodegradable, nor are most of the pigments
contained in Crayola sidewalk chalk. Also, product
packaging warns of colorants that may stain. This could
be a good factor depending on the exact nature of what
you are trying to do. While packaging does warn of
colorants that may stain, chalk used outside generally
washes away because of extreme weather conditions and
excessive rain. Again, this could vary depending on the
surface it is applied to." |
