silver bath ph HELP!

[scratched&grainy]

I am trying to make collodion negatives and have made up the collodion ok and also the silver bath. Then, according to recipes on the net, i added nitric acid to change the ph from 4 to 6. After addind the nitric acid it went down to 2! Help! What should i do? I need to make the silver bath more alkaline, right? How? Thanks,
Mark

 

[scratched&grainy]

Ok, ive looked this up the net and apparently you can add sodium carbonate to increase ph and its fine. But can you add sodium bicarbonate? As in - baking soda.?cheers, m

 

[Andrew Moxom]

You added an acid to the silver, versus a BASE. So not unusual to see Ph drop. You need a BASE/alkali to increase the ph to more neutral. Ammonium hydroxide is the best way to neutralize a silver bath, sodium carbonate will fizz and, bubble up a lot. It can also take out silver. Ammonium hydroxide does not fizz and is easier to use.

 

[scratched&grainy]

Aye. I added the bicarbonate and got a froth and some greeny-yellow gunge which i take it is the ruined silver. So ammonium hydroxide it is. Thanks

 

[scratched&grainy]

Actually, i have just done a litmus test by putting the strip of paper into the actual 1 litre bottle of silver nitrate solution which is my silver bath and the top part of the paper (surface of liquid) is ph 3 whereas 2 cm lower it is ph 6.5. So, i could just siphon off the top and be left with the ideal solution for negs?

 

[Andrew Moxom]

Yes, the frothy gunk needs to go . Filter it well..... Re-check ph, check SG and add more silver nitrate if needed to bring specific gravity within specs. My guess is you will likely need to add silver nitrate as the sodium carbonate tends to eat some.... I only used it once, and due to the mess, silver loss, now I only use ammonium hydroxide. It's stinky, corrosive, but works very well. If you need to reacidify after a neutralization step, use concentrated nitric acid to bring PH lower to if you need to go to back to making positives, versus negs.

 

[scratched&grainy]

Thanks. The ammonium worked a treat.how soon do you have to add more silver nitrate? Doing 5x4 plates for example? Thanks