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.

][<

--
To terminate puerile preservation prattling among pals and the
uncoffee-ed, or to change your settings, go to:
<http://listserv.icors.org/archives/bullamanka-pinheads.html>