Brian,
There certainly is an environmental/geographic relevance to materials.
Some bright grad student could do a thesis on that topic alone.
We work in the NY area w/ a consultant out of Dallas and for the longest
time I could not understand why they did not like urethane sealants. I
have used them for more than two decades here and have found them to be
relatively easy to use, the mechanics understand them for one thing, and
as far as I can tell they are durable. Good adhesion metal, glass and
masonry without need for a primer. We always had a bias against silicone
sealants as they were not particularly easy to use compared to the
urethanes... but I believe that has changed. We now lean towards the GE
silicones. Anyways, the reason the Dallas consultant did not like
urethanes is that in the Texas heat they would melt out of the joint.
(And immediatly after VOC reformulation we had sealant flowing out of
the joints at Sloan-Kettering that had nothing to do with heat.)
It would be nice if there was an unbiased testing of materials - sort of
like a consumer's reports for the building industry. On the contracting
end we depend on the design professionals to have sorted out their
materials. I don't think this is always the case. I see a lot of what
looks like repetition of products that comes about. I don't blame anyone
'cause I think it is human nature when pressed for time to reach for the
quick solution. Someone comes along and says, "We use Ruby Stud Glue" in
all of our histo presto projects then suddenly all the specs we get say
to use "Ruby Stud Glue." What is also always amazing to me is that the
specs will never tell us where to go purchase Ruby Stud Glue as it is
assumed that we should know everything about this wonder product.
A marketing strategy of the product reps is to get their product 'brand'
locked into the head of the design professional so that there develops a
persistence of repetition in specifications. Product reps know that
design professionals want easy pain-free answers and that if they can
get past all of the sales hurdles, the possible objections, that
eventually their product will be specified and unless there is a gross
performance issue in the field that the flow of product will be
maintained with relatively less effort. The product can be reformulated
and turn to crap on a bun but still be making money for the manufacturer
(long since bought out by a multi-national with a BOD of accountants) as
the habit of specification persists. The habit of unexamined repetition
of product specification in histo presto would also make a good grad
thesis.
At the risk of getting myself hammered -- a reason that product reps
like APT is for the above strategy (it is certainly not for the beer,
music and dancing), and as they consider that the working trades have no
influence over specification they don't get much out of PTN. Regardless
that I have seen increasingly a communication and collaboration between
the working trades and the design professionals on a per project basis.
Here is a repeatdly specified methodology that drives me nuts. For water
spray washing all the specs always say a maximum of 500 lbs p/si
pressure. I cannot get anyone, so far, to tell me where the hell this
came from. When you purchase a pressure washer it does not come with
pressure gauges. Even when you do get a guage is it 500 lbs p/si in the
hose or is it measured at the surface being washed? Most pressure
washers are rated at like 1,500 psi... does it mean you need to use a
pressure washer that only can produce 500 psi? If so, where the hell do
you get a low psi pressure washer, or a variable psi one? You don't.
(And if you can the specs never tell you where to go for them.) So let
us say that it is 500 psi applied at the surface being washed. If you go
by spread of the fan tip, say 25 degrees, generally at 6" from the
nozzle you can put your hand in front of it and not feel much of
anything. So when desk jockeys run out and say, "Oh, geeze, how do we
know that you are using 500 psi?" Usually the response is, "Look, we can
put our hand in front of it." How does that work?
I weigh in at 260 lbs and if I stand on your hand that will be like 65
lbs. per square inch, or less if you have a big hand... and you are
going to damned well know that I am standing on your hand. At one time I
was buying baby scales and having the mechanics spray the tops of them
and we were calculating the psi... if you could apply 500 psi to
limestone or marble you would blow the crap out of it. If you take a
micro-abrasive and go past 20 psi you can blow the crap out of the
masonry. (And I am always reminded of the hydro-silica machine we had at
10,000 psi that blew a hole in the brick wall when we went to do one of
our early cleaning tests with the now famous consultant/conservator
standing next to us. He was as amazed as I was. It was a struggle to
hold onto that damned thing let alone point it where you wanted it to go.)
So where the hell did the 500 psi come from? For the most part nobody
asks any questions. What it comes down to, and I have repeated this over
and over, is if the mechanic knows what they are doing, is paying
attention, and gives a crap. There is a whole set of problems with
specification of attitude and experience of mechanic and so the shortcut
is a meaningless but effective specification that says maximum 500 psi.
If you on the quality control end are on a job and you don't like what
the mechanic is doing you ask, "You are using less than 500 psi, right?"
Nobody on the craft side knows what to say and you can use the 500 psi
mantra to drive the contractor nuts until they give in, bend over and do
what you say, leastways until you walk away.
What also interests me is that all of the conservators that we run
across, and we run across a bunch of them, if you hand them a pressure
washer they have no clue as to proper methodology. We get the impression
that they are not taught how to use tools. Considering mechanics live
with their tools this modest ineptitude on the part of the conservators
instantly decreases their credibility in the eyes of the mechanics. The
one thing a mechanic will catch up on quicker than anything else is how
the other person handles a tool. So then the tool inept come out and
start yammering about 500 psi then drop their credibility when it
suddenly becomes obvious to the mechanic that they have no tactile
understanding of the tools. A skilled and experienced mechanic with a
tool is a highly refined system. Granted that the world is full of
numnuts that have no business touching histo presto fabric. Part of the
problem with all of that is that there does not seem to be any manner in
which to specify quality of the mechanic-tool system. It is forbidden...
then everyone wants to know why they are eating crap for beans on the
project.
If you look at sealants in particular as a parallel to mortars there
have been many more changes in formulation in a shorter time. We are not
now using the same sealants to replace what was used say 10 or 20 years
ago. Sealants break down and need to be replaced more often than mortar
joints wash out and need to be repointed. I do not hear any arguments
that a polysulfide should not be replaced with a urethane, though
possibly there is an SWI listserve where they do argue this for weeks on
end.
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