[pure-silver] Re: RC to FB
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Sat, 1 Jan 2005 14:26:04 -0800
----- Original Message -----
From: "Dave Valvo" <dvalvo@xxxxxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Saturday, January 01, 2005 11:26 AM
Subject: [pure-silver] Re: RC to FB
> Peter, some good questions. I did some tests about 6
> years ago sealing
> prints and running accelerated aging tests. I will share
> a few points from
> the tests.
>
> In some circumstances plastic glazing is recommended in
> place of glass. In
> fact, before I knew better, I used to recommend the use of
> Cyro OP-3 acrylic
> sheet since it was so white and clear, is light weight and
> has excellent UV
> absorbing properties. It did reduce brightener
> degradation in the tests.
> But now I know that it is also very porous to atmospheric
> gases and any
> pollutant will go right through it. I changed that
> recommendation. So if
> you have an old Kodak print storage document with OP-3 in
> it ..toss it.
> Glass is better.
>
> There is a mat product called "Artcare" produced by
> Bainbridge. It has
> molecular sieves that absorb bad gases and thus protect a
> print. The tests
> I ran did not stress the mat board enough so I can't claim
> if it helps or
> doesn't. Bainbridge tests however make the product look
> good. The boards
> are made of alpha cellulose not cotton rag. ( although
> they may have
> extended "artcare" into their cotton rag products by now.)
>
> NOTE: Red spots are seen in RC papers and are caused by
> peroxides generated
> by the TiO2 in the resin layer. The peroxides attack the
> silver causing
> shiny spots.
>
> Some points from the tests are:
> * 28 day test will cause red spots in papers without
> antioxidants. (means
> the test works)
> * Mechanized process is worse than tray processing for red
> spots and OB loss
> in RC papers.
> * Fiber base papers are not susceptible to red spots.
> * Red spots did not occur on untoned Kodak and Ilford pa
> * Selenium toning eliminates the concern for red spots in
> all papers, even
> those without AO's.
> * Wrapping in aluminum had no affect.
>
> * OB loss due to exposure to light is worse in RC papers
> than in FB papers.
> Kodak and Ilford papers were best.
> * Selenium toning does not reduce OB loss.
> * OP-3 reduces OB loss.
> * Artcare did not reduce OB loss.
>
> * Silver in RC and FB will oxidize due to atmospheric
> gases, such as paint
> fumes, new rugs and pollution.
> (previous tests showed 30 day waiting period is
> required after
> painting a room before re-hanging silver artwork,)
> * Selenium toning will protect images in both RC and FB
> papers from
> oxidation.
> * OP-3 is not as good as glass protecting images from
> atmospheric attack.
> * Artcare ability to absorb bad atmospheric
> gases...inconclusive.
>
> * Crazing concerns in Kodak and Ilford RC papers seems to
> be eliminated.
>
>
> Dave
>
This is interesting info. I think there are glasses made
with UV filtering coated on. OTOH, the purpose of optical
brighteners is to fluoresce under UV so if the UV is
filtered out of the illumination the brighteners have no
effect. For instance, compare papers with and without
brighteners under tungsten light and fluorescent light or
indirect daylight. Under tungsten light the two will look
very much alike. Under fluorescent light or daylight the non
OB paper will look dingy.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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