Kallitypes and buffered papers

[henrit]

Hi, folks,
Let me introduce myself: I'm an anesthesiologist and amateur photographer, born and living in northeastern Brazil (bright sun all year round), and quite interested in alternative photography processes, starting with cyanotype and kallitype.
Now let me bring you my first question, certainly the first of many others to come: would a well processed and toned kallitype eventually fade if printed on a buffered paper? Should we acidify buffered papers, or avoid them altogether, when working with kallitypes?
I thank you all in advance and wish you a great New Year.

 

[J 3]

Buffered papers are usually a problem for silver chemistry. The buffering often interferes with the image formation. People will sometimes soak a buffered paper in a mild solution of vinegar and then wash it out if they want to use it with buffered paper. Cyanotype is not nearly so sensitive to the paper type for good results. Somewhere on the internet there is a master paper list for papers that are known to work for various alternative processes. As for fading, yes a kallitype would fade unless toned or hermetically sealed. The image is colloidal silver and quite unprotected. If left un-toned, the silver will oxidize fading the image. Toned Kallitypes can be quite lovely. I'm a fan of theorea gold toned Kallitypes but selenium toner is easier to come by.

 

[J 3]

P.S. If I were doing a finished piece I'd stick to unbuffered papers of higher quality unless the effect I was looking for was only available in a buffered paper. For practice, or experimentation I wouldn't hesitate trying to get whatever to work. What I wouldn't do personally is invest in a large amount of buffered paper for alternative process work. It's IMO better to avoid the hassle without a good reason not to.

 

[Herzeleid]

The problem with buffered paper is that it will react with ferric oxalate as well as silver nitrate. Although many complex reactions happen inside the paper i will just focus on one. The paper buffer is calcium carbonate, so you would end up having ferric carbonate and respective carbonate salts of other ingredients. Ferric carbonate quickly oxides when it dries and you will have hydrated ferric oxides in your paper. This will damage printing quality, as well as toning.

As long as there is iron residue in a kallitype print it will fade regardless of toning, sealing or buffered enclosure. Leftover iron is the problem with kallitype and buffered paper.

Neutralize paper buffer with an acid if you need to use buffered paper, or choose an unbuffered alternative. And most importantly make sure your print cleaning process is adequate, mask the edges of your print process it, clear it. Re-expose it or leave it under the sun to check if the masked edges remain clear paper base.

 

[henrit]

Thanks, J3 and Herzeleid. I wil l try sulphamic acid, which is said to be the best option to treat buffered papers, due to its non-corrosive nature. Other acids I've tried, like muriatic and citric acid, seem to have an erosive action over the paper. I guess the best thing to do is using only unbuffered papers, by that is getting harder with current industry trends.

 

[henrit]

Well, it seems I must face the fact that finding unbuffered papers became a virtually impossible task, at least in my local marketplace. That leads to the next question: does anyone know any reasonably simple chemical test (one that can be performed by a not trained person and doesn't demand sophisticated equipment) to assess whether the paper buffer has been properly exhausted by an acid bath? Without such a test we're pretty much taking for granted what we expect to result from an acid bath, which seems not enough for me - unless some authority can tell us which acid bath does and which does not work.

 

[Herzeleid]

Try bromocresol purple indicator. One drop on the paper if it turns purple it is buffered, if it stays orange it is not buffered.
Or drop it in to a strong acid if it bubbles, acid-base reaction happens therefore it is buffered.

Acid for neutralizing buffer.
https://www.photrio.com/forum/threads/sulfamic-acid-for-paper-acidification.102747/

 

[henrit]

Thanks so much, Herzeleid. I'll get it right after the holidays.