[Alt-photo] Sodium Thiocyanate For Fixing Out Lumens

Ryuji Suzuki rs at silvergrain.org
Mon Aug 21 18:41:48 UTC 2017


When dry, hardened gelatin and unhardened gelatin have nearly identical 
behavior. Only when the gelatin is swollen, hardening makes the 
difference. (The word "harden" is probably not a very good choice but 
that's what we are stuck with.)

Wax seems to be an excellent barrier to moisture, especially compared to 
gelatin (which is only a very weak barrier). So, is this a good practice 
and recommended? I'm not sure if that's the end of the story. Material 
compatibility should be looked a bit more closely and in all sorts of 
scenarios before recommended for practice. There may be several 
questions like: is the wax pure enough that impurities will not impact 
the silver image? Is wax good enough barrier to peroxide gas? Is wax 
stable for many years in normal display condition?

Usually, we may not know historical materials that didn't work very well 
because they probably wouldn't survive. One relatively recent example of 
seemingly good idea that created a new problem is titanium white pigment 
used in RC paper. It is very bright white pigment, and it is archival 
quality but it generated oxidizing agents when exposed to light and 
untoned silver image deteriorated, but only when the prints were sealed 
in a frame or container.  Another example is acetate film base. Acetate 
film base deteriorates faster when stored in closed containers, and it 
is very important to let the film breathe in cold dry air to ensure long 
storage life (Tri-acetate is better in this regard, but many tri-acetate 
bases, especially early ones and ones from less sophisticated 
manufacturers are more like 2.5-acetate rather than 3-acetate). Some 
dyes used in color materials also keep better in presence of fresh air 
than closed or vacuum environment. So, it is not always a good idea to 
seal everything.

If you work with printed out silver image, prefer not to tone, and 
currently having less than ideal image stability, I'd once again 
recommend silver image protecting agent that acts on silver directly 
without altering it. In my experience with silver image, even a simple 
treatment with 2-MBI or PMT increased the image durability in high 
humidity peroxide gas, and these treatments do not alter the image or 
the print surface. 2-MBI is cheap and traded in massive quantities. You 
might want to test with your material.

Ryuji Suzuki
"Don't play what's there, play what's not there" (Miles Davis)

On 19 Aug 2017, at 1:05, Serdar Bilici wrote:

> Ryuji
>
> Does the  gelatin as a protective layer needs to be hardened ?
>
> What about waxes for making a protective layer? I tested the waxed 
> salt
> prints by putting them in iron blue toner, the waxed areas don't even 
> get
> wet.
> I was thinking that wax on print creates an excellent air and moisture
> barrier.
>
>
> Regards
> Serdar
>
>
>
>
> On Sat, Aug 19, 2017 at 1:38 AM, Ryuji Suzuki via 
> Alt-photo-process-list <
> alt-photo-process-list at lists.altphotolist.org> wrote:
>
>> In silver-gelatin prints, plates and films, silver image is suspended 
>> in
>> gelatin layer, which acts as a weak barrier between the air and the 
>> silver
>> image, as well as holding the image mechanically. In most modern 
>> silver
>> imaging materials, there is a clear gelatin overcoat that does not 
>> hold the
>> image.
>>
>> In salted paper print, this binder is absent. Silver image is almost
>> directly exposed to the air.
>>
>> I would expect salted paper print to be more vulnerable to airborne
>> oxidative attacks than silver gelatin IF other conditions are equal
>> (including the silver image morphology, residue of any processing 
>> chemical,
>> etc.). If you were to apply an image-protecting treatment to salt 
>> prints
>> anyway, it's probably a good idea to include gelatin or polyacrylates 
>> or
>> some other binder blends that are used in manufacturing of silver 
>> gelatin
>> materials. Whether additional binder layer will significantly 
>> increase the
>> protective strength when applied to albumen or collodion materials, 
>> it's
>> not easy to predict. In collodion plates, albumen prints, etc., there 
>> is at
>> least some binder that holds the image. I don't recall a research 
>> that
>> studied relative magnitudes of the protection of each material type.
>>
>> Ryuji Suzuki
>> "Don't play what's there, play what's not there" (Miles Davis)
>>
>> On 18 Aug 2017, at 18:03, johnbrewerphotography at gmail.com wrote:
>>
>> Ryuji
>>>
>>> Would that apply to other colloids such as albumen?
>>>
>>> Sent from my iPhone
>>>
>>> On 18 Aug 2017, at 10:40 pm, Ryuji Suzuki via Alt-photo-process-list 
>>> <
>>>> alt-photo-process-list at lists.altphotolist.org> wrote:
>>>>
>>>> Ryuji
>>>>
>>> _______________________________________________
>> Alt-photo-process-list | altphotolist.org
>>


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