Re: How to tell if a document is 6 years old...?


Richard Schultz a écrit dans le message ...
In article <1185956515.162046.239590@xxxxxxxxxxxxxxxxxxxxxxxxxxx>, Martin
Brown <|||newspam|||@nezumi.demon.co.uk> wrote:
: On Jul 31, 9:40 pm, Julian <julian.bor...@xxxxxxxxx> wrote:
:
:> How can I tell if a laser-printed (or inkjet-printed) document is 3
:> months or 6 years old?
:
: Short answer is that you can't, at least not without spending insane
: amounts of money, and even then it is doubtful. You would be down to
: looking for inconsistencies in the printing technology, toners and
: dyes available at the time. Forensic changes in the paper and dyes/
: toner with elapsed time. Degradation of printed documents depends
: sufficiently on ambient conditions like moisture, light, ozone that
: you are probably on a hiding to nothing. You could carbon date the
: paper, but any half competent forger would choose old paper or media
: so again you are stuck. And a really competent one would print it on
: contemporary period kit and accelerate the aging a bit on a windowsill
: or environmental chamber.

Neutron Activation Analysis can tell whether a document is 1 year old
or 100 years old from the depth to which the ink has soaked into the paper.
I don't know if it can tell 3 months from 6 years, though. What about
LIBS?
That can measure differences of on the nm scale, which could measure the
amount to which inkjet printer dye had soaked into the papers. I don't
know off hand if it's sensitive enough to measure the difference in the
oxidation of paper 3 months old vs. 6 years old.

-----
Richard Schultz schultr@xxxxxxxxxxxxxx
Department of Chemistry, Bar-Ilan University, Ramat-Gan, Israel
Opinions expressed are mine alone, and not those of Bar-Ilan University
-----
"Logic is a wreath of pretty flowers which smell bad."




"Neutron Activation Analysis can tell whether a document is 1 year old
or 100 years old from the depth to which the ink has soaked into the paper"


I tried to explain that one time to a professor of chemistry who works at
an university In New York
state USA. He never understood the relationship between ink on paper or
parchment and the principles of chromatography. To this day he claims your
above statement cannot be true!

JL


.

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