Sodium carbonate OR sodium bicarbonate OR does it matter?

[ColinRH]

Going through my salt printing process and checking the chemicals I note there seems to be either a typo or difference of opinion.
In the fix recipe for salt printing some list sodium carbonate whilst others list sodium bicarbonate to be added to the sodium thiosulphate.

I have looked on the net and see that the two chemicals are similar but quite different; is someone able to say which would be the correct chemical to use?

 

[Gerald C Koch]

The two chemicals are very different particularly in their basicity. A 1 % solution of sodium carbonate has a pH of 11.3 while a similar strength solution of the bicarbonate has a pH of 8.3. So the two chemicals are not interchangeable. I am unfamiliar with your process but it appears that you need to do some more research.

 

[ColinRH]

Gerald, thank you for your reply.

My question is due to the inconsistency of information I have found.

Christopher James states sod. carbonate
James Reilly states sod. carbonate
Wynn White states sod. bicarbonate

Could Wynn White's recipe be a typo? http://www.alternativephotography.com/wp/processes/saltprints/a-dash-of-salt

If the wrong chemical was used, how might it affect a print.

I understand your caveat of not knowing the process.

 

[pdeeh]

Gerald's countryman Mr. Emerson did say that a foollish consistency is the hobgoblin of little minds ...

Not surprising to find that there are varying recipes for something connected with salt printing, of course.

Crawford (Keepers of Light) only mentions carbonate and then only if using an acid fixer, while Farber suggests to use either, or indeed to use ammonia.

The latter states that the purpose of adding an alkali to the fixer for a salt print is to reduce the bleaching effect the fix can have on the print.

Like all things salty, I'd suggest experimenting to find a process and recipes that suit you, as there isn't such a thing as a "correct" answer.

With a bit of luck, we'll have a bright dry winter and we can all get the contact frames out into the back garden ...

good luck!

 

[NedL]

For fixing salt prints or calotypes, I mix the amount I need while the print or calotype is washing. The water comes from a 500ml bottle that I've added a pinch of sodium carbonate to.

Someone else can chime in, but I fixed quite a few salt prints without adding the sodium carbonate and they seem to be fully fixed.
One day when I was fixing a calotype, I got a whiff of sulfur dioxide. Alan Greene mentions that in his book and suggests the pinch of sodium carbonate to avoid this. I've added the sodium carbonate ever since then, and since I use the same water bottle for mixing hypo, it's been used on all my salt prints since then too.

 

[NedL]

Oh yes. Pdeeh reminded me. I too have read that adding alkali might reduce the bleaching effect. When I first started I tried fixing with and without Na2CO3 and could not notice any difference, which is why I originally stopped using it. I would not be surprised at all if it does have a noticeable affect on some papers and not others. I also wouldn't be surprised at all if sodium carbonate, sodium bicarbonate or ammonia all could avoid the rotten egg problem I had when fixing calotypes.

James, Reilly and White differ on many other things too.... the "alt process" world tends to be somewhat "loosey goosey".... I totally agree that experimenting and trying out different things yourself is a good idea. A salt print is a pretty thin layer of finely divided sliver, you'll see that they disagree on the concentration of hypo too,... but I think all of their versions will work. I've seen bleaching when I leave the print in the hypo for too long, but not when I left out the alkali.

 

[Tom Taylor]

I use household strength ammonia (2 mL/Liter) in the fix to prevent the "bleach down" effect. Alternative you can also use 2 gm of sodium carbonate for the same result.

Thomas

 

[NedL]

Hi Thomas,

I literally use a "pinch" of washing soda in 1/2 liter of water, nowhere near 1g.... but then I use the hypo "1-shot".

So the next question is: does it matter which alkali we use in the hypo, does it affect the color shift that happens while fixing, and does it have any effect at all on color shift in prints that have already been toned in various ways. Also, does the concentration of the alkali relate to the concentration of hypo at all?

For me this is what is so wonderful about this process.... there are dozens of variables, they all interact with each other, and they all affect the final result. There are almost infinite ways to subtlety change the way the final print looks, and as we start to get a feel for what each factor does, we inevitably move our prints to our own unique personal taste. It's almost unavoidable that your prints will reflect something personal, and over time approach something unique to you. That's true even if you don't have a set idea ahead of time what you like... you try changing one of the factors and look at the results and then you must choose, "I like this one better" or "I like this one for this kind of picture, and that one for another", or "this imparts a certain feel or mood or character to the result, and I can push it in either direction depending on the print". But no matter what you have to make a choice when you actually make a print, so you'll move a tiny step closer to your own likes.

I know that all darkroom prints are all unique and include a series of choices. But somehow I think salt printing takes the sheer number of choices to an extreme and puts those choices right in your face... the heart of the whole process is a series of small decisions: paper, type and how much salt, additives to the salt, type and amount of gelatine, how much AgNO3 and how much acid and which acid, fume or not, exposure in shade or sun or diffused or a combination, first rinse ( w or w/o different salts ), infinite toning variations, and then fixing and maybe waxing..... your choices at each step affect the final result. Some in big ways and some subtle and they all play together!

 

[Tom Taylor]

Ned,

I've been using both household strength ammonia and sodium carbonate, mostly ammonia and haven't noticed any difference. My printing ability has advanced to the stage that when I was a print, I only coat one sheet and prepare enough chemistry to process that one sheet. For the salt print I prepare 250mL of 10% sodium thiosulfate with 1/4 mL of ammonia (or 1/4/gm of SC), and 50mL of toner(s) and 250mL of 1% sodium sulfite. I use one tray processing. Recently I tried waxing some prints not suitable for framing with bees wax and lavender oil but it didn't work out. Subsequently I read that waxing didn't work with matt paper. Just the other day I read in the new James book about spreading the wax in with your finger (I was using flannel) and the melting with a hair dryer. I plan on trying that method.

Thomas

 

[NedL]

Hi Thomas, We both have the same approach! I too use single-tray and prepare only what is needed for 1 print. I'm using ~65 or 75 ml of toner, but that's probably because I've gotten lazy and I let it sit for 5 minutes between agitation...

I've only tried beeswax and lavender oil a little, and only on 3 types of paper. On one type of paper ( Canson Universal Sketch ) it is a dramatic difference, making the darks look deeper, on the paper I've used most lately ( Lana Aquarelle ) it seems to do nothing at all, except make the prints smell nice....