Problems with Tombstone Repair
A technician who uses a non-Epoxy.com product to repair tombstones
contacted us recently looking for help with problems that he was having.
He went on to say that the epoxy that he uses never fails, but rather the
stone fails. When a secondary break occurs, the stone always re-breaks
about 2 mm (about ¾ inch) above or below the epoxy joint. The epoxy
attached to about 2 mm of the stone and holds well.
He asked if the epoxy shrinks so much that it will ‘ pull away ‘
from the stone it’s attached to, and in his case, it pulls about 2mm of
stone with it.
No I doubt it is epoxy shrinkage causing the problem. High quality
epoxy has virtually no shrinkage. It would have to be a very poor
quality epoxy to be shrinking enough to do that.
Epoxy Stone Repair. What went wrong?
The reason his product is not working is that it is too
rigid. His existing rigid material has a “high modulus of elasticity”. A
material with “high modulus of elasticity” is a material that is stiff
and/or rigid. A “low modulus of elasticity” material is semi-flexible,
and is not rigid or brittle.
Differential Timing of Thermal Coefficient Event
Smaller pieces of the stone structure (in this case a tombstone) and
pieces not in touch with the ground tend to get hotter and cooler faster
than the larger pieces and pieces with ground contact. This is called
“differential timing of the event”. For example the top of a tombstone
can be heated and cooled on 5 sides, the top and the 4 sides. The base
of the tombstone which is buried in the ground has earth or stone on all
of its surfaces. This earth and stone tends to keep the temperature of
the base more stable by insulating it and slowing the change in
temperature. This works much like the insulation in your house slows
temperature changes inside your house.
When an object like a piece of stone is heated it expands (gets
bigger). When an object cools it contracts (gets smaller). For example
100 feet of concrete will be 1 inch longer once it is heated 100 degrees
F. That is why expansion joints are cut into concrete.
In the case of tombstones all the pieces of the same type of stone
have very similar if not identical “coefficient of expansion”. Since the
pieces are positioned with potentially different timing of heating and
cooling there is a “differential timing of the event” (see above). The
result is stress areas you are seeing in the closest weakened plane in
the stone near the bond line.
Selecting the Right Epoxy for Stone Repair
Epoxy.com Product #703 Clear –
specifically designed for tombstone (monuments) and/or stone bonding, or
repair. Epoxy.com Product #703 is very strong yet it is has a “low
modulus of elasticity” (semi-flexible). The low-modulus of elasticity
helps to absorb differential movement (two sections of stone heating and
cooling at different times), making it much less likely to cause a
stress area in adjacent weakened planes.
Epoxy.com Product #703 –
www.epoxy.com/703.htm is made in clear (translucent white, like
petroleum jelly) so it makes it easy to camouflage the #703 at the bond
line. This is done by rubbing stone dust(ground off the original stone
or a similar colored stone) into any exposed epoxy material while the
epoxy is still “wet”. That way the dust will stick in the wet epoxy
making the epoxy difficult to impossible to see.
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