While I've not kept up with XRF technology--particularly with the
portable hand held models, the surface condition is very important when
doing XRF analyses. (Why not--well, I've got easy access to some table
top to whole room units that are 10-15 years old and are working away
just fine.) Going through a corrosion layer or patina will influence
the results and really reflect much as to the true alloy composition. I
would agree with it being useful for a qualitative tool
for major alloying elements, but beyond that I am quite skeptical. There
is a large literature out there--both from the archaeology side and the
hard science side of the limitation of the XRF method and what it can and
can't do.
I would also caution you against believing everything the equipemnt
manufacturers tell you also.
To get an idea of the influence of the surface condition, do a very
inexpensive experiment. Go to the local hardware store and buy some
clean copper pipe. Run the analyses on it as is. Then run the analyses
on it after you've cleaned the surface with acetone. (In most cases,
it usually has a light coating of oil). Then stick it in household
vingar for a day or two, and then lift it out and allow a patina to form
on the sruface for a few days to a few weeks. And then run the analysis
again.
Best, MEH
On 10/7/2007, "Giovanna Fregni" <[log in to unmask]> wrote:
>The data was taken using a NITON XRF anaylizer. I have a more complete paper
>that I still need to upload to the site that gives more details about the
>analysis. There is one reading for a high amount of aluminium, which
>happened when the gun slipped. There is a second reading from the haft of
>that same axe that is similar to the rest of the axe.
>The small amount of titanium is from axe 5-83-10.I wondered if the metal was
>part of the alloy by accident or if there was some other source. The
>deterioration on the surface is different than the other axes in the
>collection and I wonder how much influence smaller quantities of metal might
>have on that. Unfortunately, the university would not allow the metals to be
>cleaned or to do any analysis that would be destructive. Also I do not have
>permission to remove any corrosion. From what I was told the NITON analyzer
>does take readings from fairly far into the surface. One palstave has a
>layer of accretion in the slots which might be adhesive (and I would very
>much like to learn what that substance is), and another appears to have been
>cleaned, patinaed and lacquered, but as far as we could tell neither of
>those substances from the surface showed up in the readings.
>All of the other readings are fairly straightforward except for the one odd
>one. I suppose that there is the possibility that someone slipped a forgery
>into the collection eighty years ago, but it seems unlikely.
>
>Giovanna
>
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