D96A without Calgon

[Jarin Blaschke]

hi:

I’m wanting to test motion picture developer D-96A (Metol-ascorbic acid based). I have all the ingredients except for Calgon. If Im using distilled water, does that make Calgon unnecessary?

Thanks,
Jarin

 

[trendland]

hi:

I’m wanting to test motion picture developer D-96A (Metol-ascorbic acid based). I have all the ingredients except for Calgon. If Im using distilled water, does that make Calgon unnecessary?

Thanks,
Jarin

Jarin you realy got it.....

with regards

PS : Never use the " Calgon " used in machines :

PPS : Nice portfolio on Flickr also documentary work ?

 

[Gerald C Koch]

Kodak no longer recommends D-96a as it was unstable and subject to the Fenton reaction. Calgon won't protect it. The fallback developer is D-96.

 

[Jarin Blaschke]

Kodak no longer recommends D-96a as it was unstable and subject to the Fenton reaction. Calgon won't protect it. The fallback developer is D-96.

Huh. Interesting. Unstable, even with an antioxidant like Ascorbic acid plus all that sulfite? What is the Fenton reaction?

J

 

[trendland]

Jarin a fenton "like" (katalysis) reaction is a special form of oxidation from organic substrates with the help of lower ph . AFAIK !
I could imagine there may be an inpact when developing film with iron in the water or other metals-complexes if you use the old formulation.
with regards

 

[Jarin Blaschke]

In the context of photochemistry, the Fenton reaction is basically the accelerated destruction of ascorbates in developers due to the presence of iron/copper impurities. In home-mixed developers, these impurities can be found in compounds such as sodium sulfite, so the use of distilled/deionized water doesn't solve the problem.

So how do other ascorbic avid developers avoid this?

J

 

[Gerald C Koch]

FWIW the calgon still chelates calcium but won't help with iron and copper. Some chelating agents are much more effective agains Fenton such as pentetic acid.

 

[trendland]

In the context of photochemistry, the Fenton reaction is basically the accelerated destruction of ascorbates in developers due to the presence of iron/copper impurities. In home-mixed developers, these impurities can be found in compounds such as sodium sulfite, so the use of distilled/deionized water doesn't solve the problem.

Aha - I see so the metal complexes are not coming from the water tab -they are
within the salts (sodium sulfite for example) - what about extreme purity 99,99% - I guess this would make it much too expensive?
with regards

 

[Gerald C Koch]

Iron and copper can come from the water lines. Then too iron is often found in ground water.

 

[Jarin Blaschke]

As hinted at above, do different ph states help or hinder the Fenton reaction one way or the other? For example D96A that uses metaborate or carbonate instead of Borax?

J

 

[Alan Johnson]

Xtol msds shows 1-5% of a salt of the complexing agent DTPA which is intended to remove the ions that accelerate ascorbate decomposition.
If you wish to experiment, and can source some it could be added to D96a. IDK if the pH and activity would change.
https://en.wikipedia.org/wiki/Pentetic_acid
That may be just theoretical, it does not seem to be available for photography:
http://moersch-photochemie.de/moersch/webroot/files/Preisliste_online_Okt2016.pdf

 

[Gerald C Koch]

Some years ago Ryugi Suzucki suggested using salicylic acid and TEA to sequester iron and copper ions. This will stop the Fenton reaction for awhile. If pentetic acid cannot be found.

 

[Alan Johnson]

Yes, that might be a good option, something like the amounts of salicylic acid and triethanolamine used in DS-10 on Ryuji's archived site could be used in D96a.
http://web.archive.org/web/20080930165950/http://silvergrain.com/labs/Film_Developer_Recommendations

 

[john_s]

I'm not very up to date but I have read that the product "Calgon" is not/ has not been the same in different places and/or at different times. Sorry I can't be more specific.

 

[Rudeofus]

"Calgon", as listed in the D-96A formula, denotes Sodium Hexametaphosphate (CAS #68915-31-1, see Kodak's H2415 document in table 15-2), since that's what has been used in the commercial Calgon product these days. After much rabble about phosphates in rivers Calgon changed their product to a mix of EDTA and other compounds, so you can't mix developers with today's Calgon product. Suvatlar sells the original Sodium Hexametaphosphate version under the name "Calgon-Photo".

Calgon only sequesters Calcium, i.e. regular water hardness, but will not sequester Iron/Copper well enough to protect Ascorbic Acid. The good thing: Calgon doesn't affect pH of your solution, therefore leaving it out and using deionized water will likely work. If you use D-96A within 15 minutes of mixing in the Ascorbic Acid, you won't need sequestering agents for Iron/Copper.

If you want to properly sequester Iron/Copper, such that your developer gets decent shelf life, you have three options:

1. Phosphonic Acids like AMTP (sold under the name Dequest 2000/2006) or Etidronic Acid (sold under the name Dequest 2010 or Fotoplex 2 by Suvatlar). The latter must be used with deionized water or EDTA since it doesn't cope well with Calcium.
2. Pentetic Acid is used to keep Xtol alive over six months. It works well for Copper/Iron and Calcium and is typically available as its penta sodium salt.
3. Ryuji Suzuki's combo of TEA and Salicylic Acid, both of which are rather easily available.

All of these three will affect both pH and buffering, so you'll have to readjust your developer if you add either of these Iron/Copper sequestrants.

PS: the Fenton reaction, which quickly decomposes Ascorbic Acid in the presence of Iron or Copper ions, is not significantly slowed down at low pH. The method "split in multiple concentrates, one with developer agent in Metabisulfite, the other with the alkali", which is successfully implemented in commercial color developer concentrates, won't work with ascorbate developers.

 

[Gerald C Koch]

Not all sequestering agents work to stop the Fenton reaction. Indeed EDTA actually promotes it.

While Calgon is close to neutral in solution it does slowly hydrolyse and increase the pH. Therefore it is unsuitable for solutions intended for long term storage, ie developers.

 

[bluechromis]

Presumably there is a reason the OP wanted to make D96A which has ascorbate and Metol. Pat Gainer formulated a number of ascorbate developers that could be made with Metol.
https://unblinkingeye.com/Articles/VitC/vitc.html
These don't solve the limitations of shelf life of the stock solution. A solution could be found in developers like PC-TEA where the solvent of the stock solution is not water, but an organic liquid that does not admit oxygen which suppresses deterioration in storage. The ones of those I am familiar with use Phenidone instead of Metol. But would I be surprised if some folks have not made those with Metol, or one could experiment substituting Metol in a proper ratio to Phenidone as they are said to somewhat interchangeable.