I'll try to give some short answers, but want to avoid an endless
dialog about what is or is not. A long academic career makes me leery
of misquotes in regard to the word "radioactive". I don't need more
hate mail in my email box from this site. My prior posts were focused
on the problem: 'yellow' lenses and can they be 'cured'.
Established radiation physics and chemistry points to the surface
coating(s) - SC/MC - as the 'weakest link', thus providing insight as
to whether the yellow can be 'went' by bleaching/oxidation with UV or
removed. Susceptibility of the glass to radiation damage is orders of
magnitude less than for the organic coatings.
On Saturday, August 9, 2003, at 07:10 PM, Thomas Haegin wrote:
So you are esseantially saying that the radioactive
rare elements were not used as ingredient in the Zuiko
glass "recipe", but only in the surface coatings?
NO...... I did NOT say that. First, I don't know whether lanthanum
or actinide series elements were used in one or both. Consistent with
anecdotal and glass industry history and reported beta emissions from
these lenses, these naturally radioactive elements were used by
Olympus. Factual documentation in one of the Olympus books or web
sites should provide the specific answer. Given the post WW II
psychology in Japan, detailed information re what and how much may
remain proprietary. In general, these elements were used in glass AND
in specialized optical coatings throughout the industry. My focus - -
- "Pepsodent for yellow Zuikos"!!!
I
previously thought these elements were used to
"enrich" the "glass soup" in order to achieve the
whatever superior glass qualities required for 1.2 and
1.4... but yeah, I sure could be wrong.
You are NOT wrong. For spy satellite and other extreme optical
applications, I'm confident the use of rare earth optics continues.
And if these elements are in the coatings only, and
were used in MC coatings rather than in SC coatings,
why do the early 1.2 and 1.4 yellow as they were all
SC in the beginning anyway?
See the reference I posted. As is well known, optical coating
technologies were a product of 'cold' war research and constantly
changing. Providing "1.2 or 1.4" says nothing about the specific
coating used for a given lens on the day it was manufactured. Also, I
tend to interchange MC and SC when thinking about the coating. If one
surface it was SC. Newer technology enabled use of these coatings on
multiple surfaces, MC. Not to my knowledge is there any sharp
demarcation in the coating materials used in the evolution from SC to
MC.
Or did they have some
"special" SC coating formula?
Your last sentence is the key to understanding. Make an analogy to
varnish. Most of us at least can remember yellowing of varnishes
applied as a thin coating to wood. With the advent of polyurethane and
other related chemical technologies, a clear varnish coat now remains
such for years. Remember that the first 'SC' coatings might have been
"special" in their day, but they were still in an era of yellow varnish
technology. Now varnish is mostly 'sticky broth', i.e. binder which
holds a small amount of the key substrate. Same with optical coatings.
.......and, like varnish, these binders have undergone marked
improvements.
Now for the 'radioactive' damage part. As stated, glass is notably
resistant (NOT immune) to damage from ionizing radiation (including UV
and cosmic and x-ray and.....). Coatings even without the presence of
ionizing radiation tend to 'yellow' from degradation of the organic
molecules. Full circle to where the rare earth element is located,
glass, coating or both?? At this point in time (maybe not fifty years
hence) the damage is primarily confined to the coating. So you find a
reference that says these elements were never used in the coatings.
The molecule thickness coatings are going to experience essentially
the same damage whether the emitted radiation (for practical purposes,
that of beta and alpha particles) originates from within the coating or
from the adjacent surface layer of the glass or both.
To repeat for emphasis: I do NOT know whether the rare earth elements
in the Zuiko technology were incorporated into glass or coatings or, as
most likely, both. The pragmatic issue makes this issue moot. The
'yellow' at this time is almost certainly (should be a hard science
report somewhere) in the coating. Assuming this is is analogous to
'yellowed varnish' provides insight as to 'clarifying' options. Each
to their own, but if this 'mad scientist': I would seek to disassemble
the lens and remove the coating by solvent or polishing methods - - use
care not to inhale or ingest the debris. (An alternative would be to
send to the Wyoming hashish factory.) Be aware that UV treatment also
effectively destroys the MC / SC, whatever along with the 'yellow'.
THEN- - - I would find a custom optical coatings firm to apply modern
MC. You would end with shiny white teeth, optics the equivalent of a
250/2 and bankrupt.
Let me be emphatic: if not in the coating, do NOT expect UV / dba
sunlight, to cure 'yellow' if confined solely to the glass. AMEN.
Hope that helps. Will try again if needed.
Bill
Thomas
--- whunter <whunterjr@xxxxxxxx> schrieb: >
Ahhhhh Ha...... Exactly!!!! Just posted re this
fundamental issue.
ONE: degradation is primarily in the organic
binder substrates of the
coating NOT the inorganic matrix of the glass. TWO:
whether induced
by ionizing radiation of 'radioactive decay', HEAT,
cosmic radiation,
etc., you see the effects of degradation in the same
end results.
Given a constant level of ionizing radiation (UV,
radioactive, cosmic,
visible light spectrum, whatever......) the
degradation rate of the
coating will vary greatly depending on ambient
temperature AND
HUMIDITY. All of this is additive. As you
appropriately remind, the
differing degradation of the same lens reflects
changes in additive
contributions from the environment. Further, since
the exterior of the
lens ( the coating surface) has greatest exposure,
virtually all of the
observed changes are limited to that molecular
level, NOT the glass.
__________________________________________________________________
Gesendet von Yahoo! Mail - http://mail.yahoo.de
Logos und Klingeltöne fürs Handy bei http://sms.yahoo.de
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|