In a message dated 3/31/05 7:19:23 PM Eastern Standard Time, ejw13(a)ccrtc.com
writes:
-----------------------Original Message----------------
Did you catch the news today where officials were cleaning the
memorial
that
was vandalized over the weekend with power washers and a soda/water
solution?
Joan,
Is the Memorial Limestone, Marble, or Granite. Granite can be cleaned
with a power washer, up to 2500 psi, but I don't have the Hardness chart handy,
but some Newer Marble can also be Power washed as long as you don't stand in
one spot, keep the wand moving, but power washers up to 2500 psi are also very
iffy on New Indiana Limestone, but NOT ON OLDER LIMESTONE THAT IS MARBLEIZING
OR "SUGARING". It will disintegrate completely.
I have samples of all of the above and have put them to some really
horrific tests. Personally I don't recommend any kind of Power Washing on
anything but GRANITE, and MARBLE with the MARBLE not exposed to the weather for more
than 25-50 years. I clean the black stain off of "Bedford" limestone
all of the time, but it is not exposed to the full weather like Tombstone's,
which are exposed on all 4 sides. Stone Houses are only exposed on the
Exterior surface.
I hope this helps someone that has not Pressure Washed to decide if
they want to try it or not. I have every type of construction Masonry product to
practice on. I try to see if they will damage with pressure from 1700 psi to
4500 psi. Actually 1700 is the safest, but everyone says this is to slow. It
boils down to the old "If this is good, that would be better". If you don't
know
how, or have any doubts, DONT.!!
Jack E. Briles Sr.
Floyd Co. Coordinator INPCRP
PO Box 444
New Albany, In. 47151-0444
(812)282-6585