Wet Plate Collodion – silver-nitrate bath pH problem resolved!
Recently I’ve noticed that I have a problem with silver-nitrate bath in my Wet Plate Collodion photography. I’ve done a successful portrait of Neža Peterca for Mladina weekly and then I’ve made another one of Damjan that was assisting me and this thing happened! I know this edge of fog is because of uneven dipping to the silver-nitrate solution, but if this happens only “boiling” bubbles occurs and not this fog! Than I noticed that the fog is also on the Neža’s portrait! And also on other portraits! Oops!
I_knew it’s a pH issue in my silverbath, but I had two or even three litmus papers and each of them was showing different results. I had enough of this and I’ve bought an electronic Ph checker and also a buffer pH4. I calibrated my checker so it was exact on two decimal numbers! No pH will mess around with me, I tell you! The measurement was shocking. My silver-nitrate bath was 2,2pH and it should be pH4!I’ve read Timmerman’s post on maintinace of AgNO3 bath, so I was going to cook! I evaporated 80% of solution and then I add fresh water, hoping that will fix the pH issue. It was better, but far from the wanted result. My AgNO3 solution was pH 2,8, but it was really clear (after I filter it) and real beauty on which I was resting my eyes! I know it sound weird, but wetplaters we find beauty everywhere.
The issue of pH was still there, although my plates were good for my standards and I never had them so clean :-) Check my first picture below. I’ve bought 10 ml of concentrated ammonium in a local drug store and I add only on small drop to 350ml of AgNO3 solution and the effect was immediate, from 2,8 pH to 3,8pH. Then I redid the test and results are published and commented bellow.
Conclusion: The boiling of AgNO3 did dramatically purified this solution. The raise of pH from 2,8pH to 3,8pH made my emulsion more sensitive to light and that’s for about 1,5 step. I’m not sure that those small lines on a plate are also caused by a low pH, but now they are gone! A small step for photography, a giant leap for me ;-) More about my work on www.borutpeterlin.com