Salt Printing - Staining or Fogging?

[UKJohn]

Hi,

Before I continue I have researched the existing threads relating to what I think is the problem and have adjusted my practice accordingly, but the problem still exists.

So here it is...

I am experiencing a grey stain (or maybe fogging) around the print area, which is only evident on fixing and final washing. No stain is obvious during inspection of the print at exposure stage or in the inital wash.

I am using 10 x 8 negs and a Bostick & Sullivan contact frame with a mask made from heavy black paper to give a neat straight edge slightly bigger than the neg itself, i.e. the brushed edge has been eliminated. That is, until fixing and final wash when a grey stain matching the sensitised area covered by the mask becomes visible!

As I thought this might be a fogging or contamination issue I went back to basics, bought trays and dedicated them to each stage of the process, bought glass cookware jugs, bought plastic spoons etc etc (I have also ordered glass chemical mixing rods). I even realised the kettle I used for warming up the distilled water to mix the gelatin was filthy with limescale, dumped this and started using the micro-wave. I think I could be becoming paranoid.

Although I am being extra careful with cleanliness and hopefully removing all sources of contamination a problem still exists, of course I could revert to brushed edges but I'm concerned this staining might dull highlights.

Just for information my receipes are:

Salt Solution: 12g gelatin, 36g Sea Salt (no additives), 1ml of 1% potassium dichromate, 1800ml distilled water.

Silver Nitrate Solution: 12g Silver Nitrate, 50ml distilled water and 6g Citric Acid, 50ml distilled water. Mixed as two seperate solutions and then combined.

The paper is salted in a tray whilst the sensitiser is brushed on.

The Fix: 75g Sodium Thiosulphate, 6g Sodium Carbonate, 1500ml Tap Water

The initial wash in tap is 5 - 6 mins, if gold toned this has been for 10 - 15mins, the fix is 5 mins and final wash in tap water is 30mins. I even soaked in a salt solution for 1 minute prior to the initial was but the problem still exists.

Any thoughts, recommendations or solutions would be most grateful.

Many thanks John

One last thing, I am happy to post a print for you to view if this would help.

 

[smieglitz]

John,

John Schaeffer adds a rinse step followed by a second (flotation) sensitizing step in 1% silver nitrate in his salt process. IIRC, he first float sensitizes in 12% AgNO3, rinses the sensitized sheet in several changes of distilled water before drying it, and does a second sensitizing step with 1% AgNO3 to ensure an excess of silver salt. The rest of the process is standard. You might try that approach. It really helped the last few salt prints I made to come out with less fog. (Seems I always have a little.)

The addition of citric acid also probably helps, but I don't understand why you have potassium dichromate in the salt solution. I would think the chromium salt would interfere with the speed and contrast of the silver sensitizer producing extended exposures and lower d-max.

There also may be something funky in the sea salt so regular sodium and/or ammonium chloride might produce more consistent results. Also, you might try knocking back the salt content from 2% to 1.5% to see if that makes a difference.

Maybe try a two-bath fixing step. Just thinking out loud....

What paper are you using?

And yes. I'd like to see an example.

Joe

 

[juan]

A local university professor has made salt prints for at least two decades. He insists that ammonium chloride is the only salt to use. I haven't yet tried it.
juan

 

[z-man]

please try this

ukjohn-

if this only occurs when the "dark paper " is in contact with the sensitized support you have found the source

paper that is not purpose made for contact with light sensistized materials will contain ingrediants that can cause all maner of troubles-esp fogging and staining

please try using an inert material such as mylar/polyestar/whatever against the sensitized paper----clear film between your"dark paper" and the support would do

purpose made masking material-"golden rod" paper, mylar stripping/masking support, rubylith, amberlith, lithographers ruby tape etc will all do what they were made to do

"dark paper" will do what it was made to do-- whatever that was

sea salt is remarkably consistent and so is table salt-except that table salt contains sugar and many other additives-read the fine print on the label

here in the states "diamond crystal kosher salt" is the only salt that contains only salt

i find that remarkable

vaya con dios

 

[UKJohn]

Many thanks for your replies, all are appreciated.

Smieglitz - John Schaeffer's approach sounds interesting, although it could exceed my current budget, nonetheless I will have a look at this. Just for information the Potassium Dichromate is added to boost contrast, unfortunately I cant find my notes on this but basically if it is added to the salt solution it is meant to aid in the seperation of tones whilst if added to the silver nitrate it helps contrast. This comes from an article titled 'A dash of salt' by Wynn White on the Alternative Photography website.

I have found that the citric acid, well I am assuming its the citric acid, settles out over a few weeks from the silver nitrate and forms a crust on the bottom of the bottle. Any clues or experience of this?

Juan - When I embarked on the salt priniting process and purchased my first batch of raw chemicals it did include 100g of ammonium chloride but I have to confess I've never actually used it - perhaps I should give it ago.

Z-Man - Interesting you should pick upon the mask, which is made from thick black paper or even thin black card, the use of dark paper was a mistake on my part so apologies for the confusion. I did think of this being a possible source and will change this, previously I have used the heavy black bag from a box of Ilford paper and experienced exactly the same problem, but put this down to the lack of clean trays etc in my Uni darkroom.

The sea salt I use is organic and according to the ingredients it only contains salt, I have ordered some 'pure' Sodium Chloride to see how this fares.

Anyway, many thanks for your input and it has given me a few things to think about, I'm waiting on some new silver nitrate to arrive once it has I shall crack on and hopefully solve this problem.

Cheers and thanks

John

 

[smieglitz]

...
I have found that the citric acid, well I am assuming its the citric acid, settles out over a few weeks from the silver nitrate and forms a crust on the bottom of the bottle. Any clues or experience of this?

This might be silver chloride. One of the problems of brush sensitizing (I think) is picking up chlorides in the brush and dragging them back to the sensitizer bottle/tray where they react with the silver nitrate. I think flotation largely avoids this problem and keeps the formation of silver chloride on/in the paper. But, that's all conjecture on my part.

Joe