Silver Nitrate/Citric Acid Shelf Life

[Tom Taylor]

It's been a while since I made a salt print and yesterday I spotted a subject that I think would look best printed as a salt print. I have a 11% SN solution with 5% citric acid added as a preservative. The solution was first mixed using distilled water in August, 2015 and stored amber bottle in a dark relatively cool place. The acid has precipitated out of solution and appears in a solid form at the bottom of the bottle. My question is whether the precipitated acid has adversely affected the silver solution? I am not interested in the preservative effect of the acid as I print within 2 hours of coating.

Thomas

 

[Herzeleid]

Depending on the heat and humidity silver coated and slightly buffered paper can darken spontaneously in less than an hour. It happened so I started using acid in printing. The silver citrate precipitate won't harm your solution but you have lost some amount of silver, it is no longer %11 percent.
Silver nitrate and citric acid can be mixed just before coating the paper. Into a shot glass for each 1ml of Silver nitrate add a drop of concentrated Citric Acid. I prefer to use %50, 20 to 40 percent is quite enough.

 

[Tom Taylor]

I was thinking that some of the silver adhered to the solid acid but I imagine that the solution is still good. When I first started with the process I added the acid because I was coating and drying 2 to 3 sheets at a time keeping the coated and dried sheets in a paper safe while I exposed and developed the other and had noticed that one sheet had darkened by the time I got to it. Nowadays I just coat one sheet and don't need the acid in the solution.

Also, I noticed that silver nitrate crystals turn from white to grey if kept in plastic white bottles that suppliers like Bostick & Sullivan now use. I switched from B&S to another supplier that still use abler glass bottles.

Thomas