Hoochie Mama is right Leland. Some of the points you've made are similar to
those I've been advocating. Dorothy Krotzer (architectural conservator at
BCA) and I presented at APT this year to that effect. The teamwork aspect
is an important part of the analysis. My favorite projects are those in
which I'm given tons of documentation and asked loads of questions. Then
the analysis becomes more than just providing a mix design but helps
document historical materials manufacture and usage as well as investigating
mixing and placement practices where possible.
-----Original Message-----
From: plz practice conservation of histo presto eye blinks
[mailto:[log in to unmask]] On Behalf Of Leland Torrence
Sent: Wednesday, January 16, 2008 2:08 PM
To: [log in to unmask]
Subject: Re: [BP] Spec Mix and local information
John,
Great points you make at the end, especially. You should know by now, no
apologies needed with this lot. Next shot, I will surely be giving you a
call. One point, perhaps reiterated, I believe every petrographic analysis
and mortar analysis, should have the input of a local preservation,
conservation or restoration expert who knows the local builders, architects
and materials that are most likely used. If you are dealing with a Douglas
Orr building in New Haven, 9 times out of 10, as the local guy, I could save
you lots of money just by looking at the building and a sample. I can give
you the mix and where to find the material. In the one out of ten (which we
had four years ago) we ended up with three different variations of similar
mortar, only one of which was the 9 out of 10. We started with a top notch
mortar analysis (a report as you describe would be professional) but had
questions on pigments and where to find materials. We were well aware of
practices typical of the masonry company and the architect, but had a major
hunt to get the right aggragates, all of which were to be found locally.
The best scenario for matching and analysis would be the analyzer,
architect, conservator, mason and a local guy at a table together to discuss
the best way to proceed. If I could count (but I only have two hands) how
much money Yale has spent analyzing mortar, sometimes from the same
building, without even looking at their own records, five years apart, or
did test upon test without sharing any of the previous information...hoochi
mama.
Best,
Leland
Leland R. S. Torrence
Leland Torrence Enterprises and the Guild
17 Vernon Court, Woodbridge, CT 06525
Office: 203-397-8505
Fax: 203-389-7516
Mobile: 203-981-4004
E-mail: [log in to unmask]
www.LelandTorrenceEnterprises.com
-----Original Message-----
From: plz practice conservation of histo presto eye blinks
[mailto:[log in to unmask]] On Behalf Of John Walsh
Sent: Wednesday, January 16, 2008 12:14 PM
To: [log in to unmask]
Subject: Re: [BP] Spec Mix
My answer is simple. There's a difference between sending samples to a
laboratory as opposed to sending them to a firm that "has" a laboratory.
Just because your Uncle Pete the butcher has a bunch of sharp knives doesn't
mean he should be performing open heart surgery in his kitchen. "The kitchen
chemistry" is exactly the problem as many so-called labs do these
hocus-pocus beaker digestions and couch their results in a fancy sounding
report with some mix design tacked on the end.
Mortar analysis should start with a positive identification of all the
original components. The only way I know of doing that is through
microscopic or petrographic analysis (not by color, hardness, "fizziness" in
a beaker, X-ray diffraction, nor differential thermal analysis). There are
geologists that are qualified through education and experience to use these
tools and ASTM recognizes that. There are plenty of us out there. After
and only after the qualitative identifications are performed can
supplemental quantitative tools be used intelligently to establish binder
chemistry, estimate proportions of known components, or investigate
secondary mineral deposits resulting from service life history.
It should be understood that these are forensic techniques and of course
there is some interpretative component. But when the analyses are performed
by qualified people, the differences in those interpretations are far more
subtle than those you are suggesting. Any good report should have a data
section that tells you what was detected using what technique. If binders
are identified, there should be a photomicrograph with a big old arrow
pointing to the residual binder grain. Chemistry should be provided as raw
data. Estimated mix proportions are calculated and the basis and methods of
these calculations should be provided. Interpretations and levels of
confidence should be presented in a separate section. Any scientific report
must have this format.
Finally, insist on talking to the person performing the analysis and feel
free to start a conversation to see exactly how much they know about
historic masonry materials in detail.
Forgive the undertone of irritation in this response. John, I don't know
what your discipline is but I'll assume for the sake of argument that you're
a preservation architect. How would you feel if a building owner said to
you that he didn't believe in using architects because the last time he used
an architect who designs strip malls, the guy had him put masonry cement
mortar all over his 19th century brownstone and it looked awful? Everyone
on this list belongs to a smaller preservation specialty within a wider
discipline. Architects and preservation architects, masons and preservation
masons. Those specialties come with a level of expertise and no one expects
black-box or turn-key solutions from these professionals. Why is there a
different expectation for materials scientists?
John
-----Original Message-----
From: plz practice conservation of histo presto eye blinks
[mailto:[log in to unmask]] On Behalf Of John Leeke
Sent: Wednesday, January 16, 2008 10:06 AM
To: [log in to unmask]
Subject: [BP] Spec Mix
>>Now what would be really interesting to me is if all those mortar
analyses could be brought together on a single database, along with
details of the masonry materials in the wall around them, the geographic
location, and the approximate date of construction.<<
What would go beyond interesting to immediately useful would be this:
Comparative analysis of the same sample from more than one lab. On one
project we had enough funding to have the same sample analyzed by three
different outfits. We did this figuring (in our naive way) that we would
get confirmation and be especially well assured of the results. We were
assured by all three outfits that the current methods and standards
would be used. We were very careful to assure that we mixed and divided
the samples equally, etc., etc., etc. Nothing could have been further
from the reality. All three were so widely different that the only
conclusion and action we could come to was to toss them all out and go
with our own usual "farmyard physics and kitchen chemistry" "seat of the
mortar-stained pants" analysis, which in the end has always been
entirely adequate. So, what I would like to see is a blind study of just
how "accurate" and "consistent" mortar analysis is. Is mortar analysis
ART or SCIENCE or something in between? Perhaps this is something like
dendrochronology was through the mid-20th century, a practice that
required so much interpretation that it was, essentially, an art. More
recently apparently statistical analysis has been applied to
dendrochronology significantly reducing the need for artistic
interpretation making it more of a practical science. So, where are we
with mortar analysis?
John
not a mason, I don't even know the secret handshake
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