Steve,
Thanks for the note on hydrofluoric acid.  I remember a couple of years
ago we used it to rinse out iron stains in a highly diluted form.  It
was very aggressive on the quartz when we first tested, but wetted and
rinsed did the job quite well.  I was working with an Australian who
warned of the health hazards and when I looked nonchalant, he raised his
eye brows and said, "No, I'm serious, this is very nasty stuff."
I was asking Ken about the calcium fluoride can you refresh us?
Best,
Leland

-----Original Message-----
From: "Let us not speak foul in folly!" - ][<en Phollit
[mailto:[log in to unmask]] On Behalf Of S.
Stokowski
Sent: Thursday, May 08, 2003 8:16 PM
To: [log in to unmask]
Subject: Re: Klenztone????


Mitch, Ken, Leland:

In my opinion, hydrofluoric acid is probably the most serious chemical
hazard in restoration and renovation.  It's danger isn't as an acid.  In
fact, it's acidity is so weak that it is fairly ineffective.   But, this
chemical can easily cause severe illness, loss of limbs, and death.
How?  The HF starves human cells of essential calcium.  It can kill it's
way to the bone in your arm or your leg, where it usually stops, causing
one to lose a limb but not a life.  Or, if you splash it on your chest,
it can just drill to your heart, whereupon the heart muscle dies just
before the mind.

Why do I know all this about HF?  I've been trained in it's hazards.
I've used it for whole-rock chemical analyses and for separating pollen
from clay and silt.   I've instructed my chemist employees how to use HF
safely and responsibly.  I've worked for a company (Vulcan Materials)
that made hydrofluoric acid.  In my opinion, HF should only be used in a
fume hood with rubber gloves, a chemical apron, and goggles.  Why
anybody without a wish to die a horrible death would use HF in the open
air without wearing a full set of protective equipment is a mystery.
Maybe they are damned fools; maybe they are the low bidder.  Maybe the
boss just figures that laborers are expendable.

I hope that everybody who has or intends to work with HF has calcium
gluconate gel and syringes in their medical kit.  These are essential to
counteract the effects of HF exposure.  I bet that nobody does.  Perhaps
I shouldn't be so cynical.

On the plus side of HF, it works fairly well to dissolve iron stains and
dust deposits consisting of quartz silt and fly ash.  It also brightens
granites and other quartzose rocks.  It dissolves the quartz and
silicate minerals preferentially at the surface fractures that make a
stone lighter than it's intrinsic color.  If the rock contains calcite
(calcium carbonate) it reacts to form fluorite (calcium fluoride).  This
precipitated mineral slightly protects the surface.

FYI, the Lincoln Memorial is made of Yule marble from Colorado.

Steve Stokowski
Stone Products Consultants
Building Products Microscopy
10 Clark St., Ste. A
Ashland, Mass. 01721-2145
508-881-6364 (ph. & fax)
http://members.aol.com/crushstone/petro.htm

****************************************

In a message dated 5/8/03 5:24:01 PM Eastern Daylight Time,
[log in to unmask] writes:



Are any of you stone guys familar with Klenztone cleaning chemicals?
One of there products uses a special formula of floride salts.


Mitch,

I'm quite familiar with the materials and have used them to good effect
but am a bit peeved about their lack of truth in advertising. Despite
the fact that the advertising states that the chemicals contain no acids
the flouride salts turn to hydroflouric acid when they encounter water.
According to my materials handbook hydroflouric acid is used in cleaning
cast iron castings by dissolving the sand from the castings. What this
means for sandstone I think should be self evident. What it means to the
Lincoln Memorial, I assume of granite, is possibly less shocking. I
would certainly NOT use it on limestone or marble. What gets me with
suppliers of chemical cleaning solutions is that they will say that
their materials were used in this place, or that, but they will not tell
you the truth of the long term results, or what is really needed to know
in order to do no harm. I feel that Klenztone is the worse of any in
this regard. In the past I've asked Klenztone (directly asked of
Klenztone and NOT of any of their suppliers who usually have no idea
what they are selling) to give us names of buildings where their
products were used in order to revisit the locations in order to
determine if the masonry was acid burned, or not. It is when
manufacturers are not up front with their information that I begin to
suspect ALL of their marketing hype. The "no acids" caveat is one that
will catch out preservationists seeking a non-acidic cleaning
methodology... well, when you use their product it does look good. It
has to be used with the same care, skill and attention as would be used
when cleaning masonry with any acidic cleaner. But if your chemistry and
science in the beginning exluded the use of acids, then I think it a
really lousy deception to pretend that acids are not being used with
Klenztone.

My first phone conversatin with Martin Weaver was to ask him about
Klenztone, and my naive remark that the material contained no acids and
I wanted to know how it could possibly clean masonry. His comment, in
brief, was that he did not know of any masonry cleaners that would not
contain acids. I went away imagining that he would think I was a
complete dolt. Some time later I spent an afternoon drinking ale with
him and Bobby Watt in a dive in Ottawa and found out Martin is a very
very nice guy, a bit hilarious in humor and an out-of-the-box free range
nut case.

][<en