[rollei_list] Re: Old film

----- Original Message ----- 
From: "Don Williams" <dwilli10@xxxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Monday, May 30, 2005 12:23 PM
Subject: [rollei_list] Re: Old film


> At 05:10 PM 5/28/2005, Dick wrote:
> . . . . .
>
>>    Silver is more stable than dye but is actually not 
>> very
>>stable unless toned. Silver sulfide is extremely stable.
>>Silver sulfide images are the result of using any of 
>>several
>>Sulfiding toners, often called Sepia toners. Kodak Brown
>>Toner and the very similar Agfa Viradon are examples of 
>>such
>>toners.
>
> I think I have a variety of prints, some of which may be 
> tintype, in a box
> I picked up from my stepfather many years ago.  I think 
> some of them are
> indeed tarnishing a bit.  Any suggestions.  (I haven't 
> even looked in there
> in a couple of years, since some of the photos were in 
> mounts and I didn't
> want to sort out the broken glass, guess it's about time.
>
> DAW
>
>
   Tintypes, more properly Ferrotypes, are photos made by 
coating a very thin sensitive layer on polished metal. Since 
silver in very thin layers is reflective, a direct positive 
is had by making the backing black. The silver image looks 
white in comparison. Tintype coating may be gelatin but many 
were also made using collodion. Restoring them is really a 
job for a professional conservator.
   Regular prints can show the effects of oxidation of the 
silver by "mirroring" or
"bronzing". This is an effect where the image silver is 
oxidized, the oxide being extremely fine is able to migrate 
to the surface where it may be again reduced to metallic 
silver by other pollutants. The result is a noticeable shiny 
area especially over the denser portions of the image. 
negatives, in principle, are also subject to this redox 
effect but the image silver grains are so much larger than 
print grains that the effect is rare.
   There are treatments that can remove the surface 
material. They consist in general of bleaching in a 
permanganate bleach and redeveloping. Any such treatment can 
destroy the print so the best procedure is to make the best 
copy negative or scan possible before trying any remedial 
treatment.
   Kodak has a couple of good books on identifying and 
preserving old images. I have to search mine out to give you 
publication data. Again, its wise to consult a professional 
before attempting anything other than copying damaged old 
images.
   I am not sure if your reference to broken glass refers 
glass slide mounts of glass plate negatives. The emulsions 
of broken glass plate negatives can often be transferred to 
a new support. There are techniques for stripping both 
gelatin emulsion and collodion (wet plate) coating but I am 
not an expert.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx

 

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