Oxalic Acid in Kallitype Sensitizer

Hi,

I'm using the following formula for kallitypes per 10gr of Silver:

152.25ml H2O
25.2gr Ferric Oxalate
10gr Silver Nitrate
1.67gr Oxalic Acid

Is the oxalic acid necessary? This is from the book Photographic Possibilities.
Also, I have been mixing the solution as a whole but I wonder if it would be better to dilute the FO and SN in different bottles and use equal parts in drops to sensitize the paper. If so, where to put the oxalic acid? Does it matter? I really want to learn more about the chemistry behind this process; perhaps someone can recommend a good book to start, considering that I don't really know anything about chemistry. I've been following recipes from books and the popular online sites but I would like to be able to experiment more without blowing up the house or creating dangerous fumes. I teach computer science so my level of math is good, if that is of any help.

Thanks

First a caveat... I do not having any first hand experience with kallitypes, but I have done other alt processes and I am a retired chemistry professor. Thus, my response is based mostly on my chemical intuition with some alt process intuition thrown in.

Is the oxalic acid necessary? Probably not, there are many other recopies for kallitype that do not include it.

Making separate solutions will probably work, many other kallitype methods keep them separate as stocks. If you are going to do this I would try to make each stock solution at twice the concentration you list. Then when they are mixed 1:1 as you suggest the final concentrations will match your original recipe. The one possible hitch in this plan are the solubility limits for the various components... one or more might not be soluble at twice the concentration list in your original recipe.

Separate solutions should be less sensitive to light than the combination. As you will see in the chemical details, all of the photochemistry in the iron-based processes begins with the photo-reduction of the iron.

If you are going to try separate solutions and want to include the oxalic acid, I would add the oxalic acid to the ferric oxalate stock and not to the silver nitrate.

As for learning about the chemistry, I would start here: https://www.mikeware.co.uk/mikeware/Iron-based_Processes.html. Mike's site is definitely the "go to" source where chemistry and alternative processes intersect.

I think that I covered all of your questions... if not, ask again!

DMJ said:

10gr Silver Nitrate

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fgorga said:

As for learning about the chemistry, I would start here: https://www.mikeware.co.uk/mikeware/Iron-based_Processes.html. Mike's site is definitely the "go to" source where chemistry and alternative processes intersect.

I think that I covered all of your questions... if not, ask again!

Click to expand...

Thanks a lot Frank. I am familiar with Mike’s site; I have to go back and read throughly. I also found out there is a printed book by him coming out soon, which is great because I would rather read text on real paper where I can write notes.

https://www.amazon.com/Platinotype-...qid=1606839217&rnid=2941120011&s=books&sr=1-2

Martin

This Sandy King article is a classic....He does not use oxalic acid in his recipe.

http://sandykingphotography.com/resources/technical-writing/the-kallitype-process

Here is another source that might be useful:

https://www.bostick-sullivan.com/articles/kallitype.html

In this article about ferric oxalate, it states that in order to check for extra oxalic acid, add a drop of silver nitrate. Based on that, it would seem your recipe would likely make white precipitates of silver oxalate - not welcome in a sensitizer.

https://www.bostick-sullivan.com/articles/ferriccoalate.html

It might be possible that the reason it is recommended to use oxalic acid in this recipe is to facilitate dissolution of ferric oxalate from powder. This could be solved by getting a pre-dissolved ferric oxalate instead (if you haven't already procured the powder that is) and avoiding the headache of trying to make the solution yourself which anecdotally has been known to be a cumbersome process.

:Niranjan.

nmp said:

This Sandy King article is a classic....He does not use oxalic acid in his recipe.
It might be possible that the reason it is recommended to use oxalic acid in this recipe is to facilitate dissolution of ferric oxalate from powder. This could be solved by getting a pre-dissolved ferric oxalate instead (if you haven't already procured the powder that is) and avoiding the headache of trying to make the solution yourself which anecdotally has been known to be a cumbersome process.

:Niranjan.

Click to expand...

Thanks.
You are probably right, the instructions for preparing the sensitizer for coating ask for warming the sensitizer in a water bath at 100F (38C) to redissolve the crystalline silver oxalate precipitation. So it might be possible that the oxalic acid helps to dissolve the ferric oxalate in water. This is from Robert Hirsch's book. It also asks for warming all the developers and I've been doing it but it is an extra step I'm not happy about.
I just read on Bostick's site the correct way to dissolve Ferric Oxalate using the microwave, otherwise it can take up to 24 hours.
I buy everything in powder form from Bostick.

Martin