Resined
slabs: The Good, The Bad and The Ugly
by Frederick M. Hueston,
Q: Our
shop has been getting a lot of resined slabs lately, and I am a little confused
as to why slabs are resined to begin with. I would be interested to know why
they are resined and what problems fabricators are having with these resined
slabs?
A: In the past few years, I have had many fabricators ask the same question. Of
all the fabricators I have spoken with, some have no problem at all with
resined slabs, while others are having nothing but problems. The following are
some of the pros and cons of resined slabs. The following article is not
intended to solve this problem or to render an opinion but to put forth
arguments from both sides. In other words the good, the bad and the ugly.
The
resining of stone slabs is not as new as some might think. Resining started
back in the 1960s on marble and about 10 years ago with granite. Today, the
resining of slabs is commonplace, and it is predicted that almost all stone
slabs will soon be resined.
What
is resining?
The resining
process uses epoxy resins for granites and polyesters for marble. There are
several methods that are used to apply and cure the resin, from hand-spray
applications to automated lines. The slabs are first honed and dried, and then
the resin is applied. The slabs are then cured in heated ovens, and after the
resin is cured, the slabs are sent to the polishing lines where they are
polished. Some factories also apply a thin layer of wax to the surface after
polishing to help protect the stone during shipping.
The
Good
The resining of
slabs has allowed slab producers to eliminate lots of waste and sell slabs that
would otherwise be rejected. Brittle materials can now be used due to the
resining process, which helps hold the brittle material together like a glue.
Resined
slabs are also less likely to become damaged during shipping.
Resining of
slabs has also reduced the price of slabs, which is one reason the industry is
seeing such a big growth in slab sales in recent years.
Resined
slabs are also less porous, and many resined materials do not need to be
sealed, since the resin acts as a sealer for the stone.
In
addition, Filippo Emanuel of Tenax
Several
materials are naturally fractured and could not otherwise be sold or marketed
even if they are superior in terms of color, durability and other qualities.
There is a
growing tendency in producing thinner slabs to reduce transportation costs and
open up new markets and different stone uses.
The waste
from manufacturing slabs of particular materials (especially some marbles)
could represent 35 to 40% of production, thus considerably increasing the cost
of the remaining slabs.
Many
different kinds of granites have natural micro-fissures that compromise the
final polished effect, thus reducing the beauty of the material.
There are
materials just too fragile to be polished, leaving no solution but to close
down quarries.
Some
granites have fissures that pass through the slab and considerably decrease the
strength of the slabs and pose a hazard when used as outside paneling.
Limited reserves
of a particular color of stone leave only the worst and more damaged veins to
be quarried.
The
Bad and The Ugly
Over the past few
years, several problems have arisen with resining slabs. The following are some
of the problems that have been encountered:
1. Fading
One of the major complaints associated with some resined slabs is that the
resins used are not UV resistant. I have heard of several fabricators who store
their slabs outside for several months, and when they go to use them, they
discover that the slabs have darkened. This is especially true of slabs that
are covered. In one case, a slab of stone was partially covered with another
section of stone. When that small section was removed, it was discovered that
the portion of the slab that was not covered had darkened. This is the result
of UV light reacting with the resin. The lesson to be learned here is not to
store slabs outdoors in direct sunlight. This is especially true of light
colored materials such as Giallo Veneziano and others.
However,
Emanuel points out that there should be no resin on the surface of the slab.
“If there is, it means that the manufacturer did not do a good job removing
it,” he said. “That is when fabricators start having problems with darkening
effects.” If done correctly, the resin is inside the cracks and the pits, but
nowhere else.
An
additional problem is with profiles. Several fabricators have had experiences
with the profiled edge turning out lighter than the rest of the stone. “The
problem with the edges is that the resin will darken the top of the slabs
regardless of the UV,” Emanuel explained. “It is just the effect of the
different reflection of the light when a material is imbibed with resin. When
you cut the edge, there is no resin on the side — regardless of the UV
exposure. That’s the reason why the edges are lighter.”
Over time,
we have found that the edge will darken and match the face of the stone. A
quick fix to this problem is to use a color enhancer to darken the edge.
2. Sealer
interaction
Our technical hotline has received several calls where impregnators have been
applied to a resined stone, and the material clouds, discolors or fades. After
testing several slabs and sealers, I have discovered that some solvent-based
impregnators will react with the resin, causing it to break down and turn
color, cloud or fade. This is a problem that is difficult to repair. We have
found that the application of a color enhancer will sometimes hide this
problem. My recommendation would be to use only water-based impregnators on
resined slabs.
3.
Polishing and refinishing problems
In a recent countertop repair seminar, one of our students brought in a resined
section of stone he wanted to try and refinish and polish. We discovered that
this material had such a heavy application of resin that when he tried honing
the top, the resin became gummy. Once the surface was cut and polished, it was
very difficult to match the remaining surface of the stone. As of this writing,
I have yet to find a solution to this problem other than to refinish and polish
the entire slab so it all has the same polish.
Please keep
in mind that that some of these problems may be the result of improper
application and not necessarily the resin itself. Just like any other industry,
quality control can be an issue, and sometimes a slab or two may slip by. This
is why it is important to deal with reputable slab distributors and to
carefully inspect each slab upon delivery.
Only time
and history will tell if the resining process is good, bad or ugly. Of course,
resin chemistry will most likely improve, as well as the application process.
In the meantime, stone fabricators should be aware of these problems and learn
to deal with them.
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