From: Richard Sullivan (richsul@earthlink.net)
Date: 02/05/02-05:32:15 PM Z
I have found neither to be true. This is both from 23 years of shipping
experience and semi-formal testing. I have baked ferric oxalate powder on a
hot plate in the 300+ Deg F. range overnight (the first time by accident)
and have boiled ferric oxalate solution (No 1. made from B+S powder) and
within the variabilities of testing against making prints and step wedges I
have seen no ill effects.
Ferric oxalate gains speed as it ages. Heat can accelerate aging. There can
be quite a speed gain before one sees any fogging. Once fogging sets in it
tends to accelerate rapidly. That is a slight fogging will quickly turn to
a rapid fogging and then wham a murky print. Powder that fogs is visibly
dirty. The amount of ferrous necessary to cause fogging causes the powder
to lose it's clear color. I have a 100 gm bottle in my lab with a rubber
stamped label, pre-Osborne computer printed labels so @ date 1980 and the
color is still bright and it is not foggy. It was stored for years in a
shed in the back of our Southern California facility for at least a decade.
I venture to say the temperature there reached 140+ for many a summer day.
In my opinion dry powder is quite stable. Had this been liquid I dare say
it would not be good by now.
I have had periodic reports from people who have accidently boiled FO and
call worried that it will be bad. These queries have been received from
some very highly respected printers and I cannot recall one instance where
they had noticed a difference after we told them it would be ok to use.
As a matter of course it is not wise to subject powder or liquid to
unnecessary heat but it is not a issue of serious concern.
However there appears to be a weird phenomenon that has not quite been
accounted for and that is the freezing of liquid FO. It appears in some
cases to form a insoluble mass after freezing and thereby becomes unusable.
I've heard form some trained chemists that it may be some form of
polymerization taking place.
--Dick Sullivan
At 04:56 PM 2/5/2002 -0500, you wrote:
>Richard Sullivan wrote:
> > ... any heat encountered during shipping will not hurt the ferric
> > oxalate to any degree that will affect its printing qualities.
>
>But I do have the prints to show this. Then again the truck in question
>(and it was a UPS un-air conditioned) was in Phoenix in the summer, so I
>guess that can qualify as "on fire". Also, subjecting the sensitizer
>solution to high temperatures (greater than 140F) can cause some
>flatness or fogging in the print.
>
>--
>Jeffrey D. Mathias
>http://home.att.net/~jeffrey.d.mathias/
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