"Ken
Follett has been involved with heritage masonry restoration for
several decades. He is a founding member and was the first president of
the Preservation Trades Network.
He
currently resides in Brewster, NY, and primarily works with his
son-partner, David Follett. They are hands-on consultants for
architects, engineers and conservators during the design phases in their
investigation of historic structures, wood, masonry, metal or
otherwise.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sharing this statement (July 20, 2014) from Mr. Ken Follett:
"I
am not a gravestone specialist, but I have been playing with stone,
and other masonry materials, professionally for more than forty years.
There is a much wider context within the stone industry as to surface
treatments, it even includes controversy over the methods of polishing
stone floors in modern buildings.
The crux of the issue here as far as materials science goes is that it is true that by polishing of a stone surface it reduces the surface area and in such reduces the exposure to erosive elements.
But this is on a scale that one would need a microscope to be able to notice. The polishing does not reduce the porosity of the stone, or the ability of a stone to take on moisture. Water tends toward an equilibrium of distribution and as such all masonry contains water, and as such irregularities in topography promotes micro-environments that can be suitable to biologic growth. The fact that a stone is polished, and the irregularities of topography reduced may decrease the frequency of micro-environments in the short-term, but it will not in the long-term inhibit continuation of erosion and a return of the rough surfaced topography and a return of biologic growth.
In minuscule respects the removal of an existing stone surface, even one that feels rough to the touch, through polishing can accelerate decay through exposure of underlying material of a softer consistency, particularly in a calciferous stone (such as marble). The difficulty is that this acceleration of degradation is not going to be noticeable in a 1-2 year span, but in the time frame of the gravestone itself that already took maybe 100 years to get to the condition that it is at now. If we wait another 100 years none of us will be around, but likely the surface of the polished gravestone will not be either.
I am a solid advocate of D/2 biologic solution, that regardless, the technique of treatment of stone surfaces of a cultural heritage value with polishing with Nyalox brushes on a power drill is totally off the charts on an international basis in the world of stone and monument conservation. Likewise the bad thinking that gravestones need to be "returned to how they looked originally". The very first question needs to be, "Why do this at all? What is the necessity? Where in our culture does this need come from?"
I am reminded that my cousin is a clean freak and she got so obsessive over keeping her fish tank spotless clean that she killed off all of her fish.
The argument that D/2 roughens the surface of the stone is pure bull pucky. The surface of the stone is rough and if you take away the biologic elements that film over the topography, and that in turn maintain erosive elements to the surface of the stone (either in inhibition of water transmission through evaporation out of the stone, which can lead to freeze-thaw capillary degradation, dependent on the climate, or secretion or containment of atmospheric or biological acids that will dissolve the stone) then of course the surface will feel rough to the hand, or in some cases to the eye. But what you have left is stone, minus the biologic element, and what you do not have is stone dust at the base of the marker, or on your hands."
The crux of the issue here as far as materials science goes is that it is true that by polishing of a stone surface it reduces the surface area and in such reduces the exposure to erosive elements.
But this is on a scale that one would need a microscope to be able to notice. The polishing does not reduce the porosity of the stone, or the ability of a stone to take on moisture. Water tends toward an equilibrium of distribution and as such all masonry contains water, and as such irregularities in topography promotes micro-environments that can be suitable to biologic growth. The fact that a stone is polished, and the irregularities of topography reduced may decrease the frequency of micro-environments in the short-term, but it will not in the long-term inhibit continuation of erosion and a return of the rough surfaced topography and a return of biologic growth.
In minuscule respects the removal of an existing stone surface, even one that feels rough to the touch, through polishing can accelerate decay through exposure of underlying material of a softer consistency, particularly in a calciferous stone (such as marble). The difficulty is that this acceleration of degradation is not going to be noticeable in a 1-2 year span, but in the time frame of the gravestone itself that already took maybe 100 years to get to the condition that it is at now. If we wait another 100 years none of us will be around, but likely the surface of the polished gravestone will not be either.
I am a solid advocate of D/2 biologic solution, that regardless, the technique of treatment of stone surfaces of a cultural heritage value with polishing with Nyalox brushes on a power drill is totally off the charts on an international basis in the world of stone and monument conservation. Likewise the bad thinking that gravestones need to be "returned to how they looked originally". The very first question needs to be, "Why do this at all? What is the necessity? Where in our culture does this need come from?"
I am reminded that my cousin is a clean freak and she got so obsessive over keeping her fish tank spotless clean that she killed off all of her fish.
The argument that D/2 roughens the surface of the stone is pure bull pucky. The surface of the stone is rough and if you take away the biologic elements that film over the topography, and that in turn maintain erosive elements to the surface of the stone (either in inhibition of water transmission through evaporation out of the stone, which can lead to freeze-thaw capillary degradation, dependent on the climate, or secretion or containment of atmospheric or biological acids that will dissolve the stone) then of course the surface will feel rough to the hand, or in some cases to the eye. But what you have left is stone, minus the biologic element, and what you do not have is stone dust at the base of the marker, or on your hands."
~*~*~*~*~*~*~*~*~
Lynette Strangstad is the author of the well-known publication:
"A Graveyard Preservation Primer" first published in 1988; and now in its second edition published in 2013
Lynette's website is: Stone Faces and Sacred Spaces
(Lynette's statment is in response to a question containing photographs of unreadable gravestones.)
"Briefly, in my opinion, "polishing" an old gravestone is not appropriate. The
entire stone is altered. Some of the surface is removed. And that
fragile surface is the very reason most consider the stone valuable. (though that is only part of the significance). In grinding the surface (that is, polishing), one is removing part of the lettering. Three
or four such abrasive cleanings (over time, say, 15 or 20 years) could
easily equal the stone loss that would occur naturally in a hundred or
more years. It's good to
remember that care for gravestones is not just to satisfy our aesthetic
desires in the present; it is to preserve the stone for future
generations. The stones I saw
in the photos are the type that can frequently be effectively cleaned
with water and a soft-bristled brush (natural tampico bristles are
best). D/2 is an effective and responsible cleaning agent, when needed."
"The
important thing to remember is that "less is more" and the least
aggressive treatment that can clean effectively is the best. Also to be
remembered is that no old gravestone should "look like new." It's not; it's historic. And it best is shown when it shows its age. Yes, I understand that reading a stone is important. An effective alternative to cleaning or polishing is to allow for reading of stones through the use of mirrors. Reading a stone with mirrors often creates a dramatically readable stone. Using mirrors, recording results both with a written transcription and a photograph, is often the best approach. The
inscription can then be read and recorded, and the stone can be
photographed. This is all effectively done without harming the stone."
Statement from Dennis Montagna - Vice President & Conservation Committee Chair, Association for Gravestone Studies:
Friday, December 12, 2014
Shared with Permission:
"We neither support nor condone the aggressive cleaning of cemetery monuments, whether through mechanical or chemical means. Moreover, in my nearly nearly thirty years in the preservation field, I can't think of a single case in which the use of power-driven brushes made sense as a stone cleaning tool. In fact, Nyalox brushes are typically impregnated with aluminum oxide abrasives, so they would have an especially devastating effect on calcareous stones like marble, limestone and some sandstones."
~*~*~*~*~*~*~*~*~
Statement from Dennis Montagna - Vice President & Conservation Committee Chair, Association for Gravestone Studies:
Friday, December 12, 2014
Shared with Permission:
"We neither support nor condone the aggressive cleaning of cemetery monuments, whether through mechanical or chemical means. Moreover, in my nearly nearly thirty years in the preservation field, I can't think of a single case in which the use of power-driven brushes made sense as a stone cleaning tool. In fact, Nyalox brushes are typically impregnated with aluminum oxide abrasives, so they would have an especially devastating effect on calcareous stones like marble, limestone and some sandstones."
Dennis Montagna, Ph.D
Vice President and Conservation Committee Chair
Association for Gravestone Studies
101 Munson Street--Suite 108
Greenfield, MA 01301
~*~*~*~*~*~*~*~*~
Statement shared with permission by Joy Beasley of the National Park Service -- Abrasive Brushes are Not Allowed for Use on Gravestones:
Sharing the reply of Ms. Joy Beasley, Chief of Cultural
Resource Preservation Services for the National Capital Region of the
National Park Service, when asked about the National Park Service's
stand regarding the use of any power tools and/or abrasive brushes on
gravetones:
"According to Joy Beasley, Chief of Cultural
Resource Preservation Services for the National Capital Region of the
National Park Service, the use of power equipment with abrasive brushes
is not allowed, since most historic stone materials are likely already
very weathered and delicate. The NPS recommends using natural bristle
brushes, and brushing very gently (like you would brush your teeth). If
there is excessive biological growth or for general soiling, they
recommend the use of non-ionic detergents or architectural
antimicrobials but they do not allow the use of bleach as it will cause
deteriorating salts to form on the stone.
Regardless
of the method, any cleaning that is undertaken on delicate headstones
can further their deterioration, so the NPS strongly recommends that
such projects be carefully planned and considered in order to minimize
adverse impacts."
Joy Beasley
Chief, Cultural Resources Preservation Services
National Park Service
National Capital Region
1100 Ohio Drive SW
Washington, DC 20242
202-619-7146 (office)
