Ammonical Silver Nitrate Brown Precipitate...

lorien barker

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Hello all,

First time posting... apologies if format is wrong.

So Im a photography student, trying his hand at salt printing. I bought the fotospeed kit and had my first go the other day. In that kit, it says add small quantities of ammonia to the AgNO3, which I did. I put it in a glass bottle to keep. (No citric acid). The kit said use 30ml per 10x8. I did so... and seemed to have HUGE quantities extra.

I came back to it a week later.. and it had brown precipitate in it. Almost like micro hairs and a few larger particles.

My question is... can this still be used if I were to filter it out? I am reluctant to chuck it... for cost and environmental reasons if it can be used... I would like to do so. Anybody know what the precipitate is, and why it formed?

I wrapped some gaffer tape around the jar, and put it in the bottom cupboard, so UV exposure should be minimal.

Also while im here.. any suggestions to prevent mottling of paper? (basically paper rubbing away). I used a foam brush and paper disintegration was evident. Just bought a softer brush to try. Perhaps I was a little enthusiastic in coating my paper....

Cheers for the help in advance,

Lorien
 

Mike Ware

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Adding ammonia solution to silver nitrate solution initially causes the formation of a brownish-black precipitate of silver oxide, which then re-dissolves on addition of more ammonia, to give a clear colourless solution of diammine silver nitrate, or "ammoniated silver nitrate" as it used to be called. It is not clear from your description and quantities if you re-dissolved all the silver oxide (which is harmless).
BEWARE !! Ammoniated silver nitrate solution (originally clear) can, over time, precipitate a dark solid called "fulminating silver", which, as its name implies, is a high explosive. See Wikipedia.
It can even detonate when wet. Contained in glass, it is very dangerous. Keep it secure, and seek advice locally from your chemistry department.
 

nmp

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I don't know why fotospeed people are pushing this method when plain AgNO3 works just fine, particularly when they are not informing fully the precautions that are needed. Please do heed Dr. Ware's advice above.

Yes, 30ml for 8x10 seems excessive - by nearly 10X.

Foam brush should not rub the paper away. What type of paper are you using?

Welcome to Photrio, Lorien.

:Niranjan.
 
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lorien barker

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Oh good start then....

Yes so I did exacly that. Added small quantities of ammonia, it precipitated out, then redissolved and stopped. This precipitate has formed in the week since.

Well thank you for your warnings! Will be taken on board. I have attached a photo of the precipitate. Didn't quite realise how dense the precipitate was until I took a flash to it. I have a feeling the bigger particles might be from the foam brush. But not sure.... Ideas? couldn't find a good picture of images to indicate if indeed ive made fulminating silver.

The paper is the one again from the kit. Canaletto 160gsm.

Thanks again for all your help!

 

nmp

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I am not saying whether or not you have the fulminating silver, but there is a possibility that it a precipitated silver due to cross contamination. Are you using the same brush for salt as well as the silver? If so, there is a possibility of some of the salt getting transferred to the cup forming silver chloride which then can precipitate silver metal over time, specially if it got exposed some, turning the solution dark. You can also transfer salt from the paper to the brush, even if you are using a separate one, while spreading silver nitrate, which then can end up in the silver nitrate container. A better way is to use a dropper to transfer the silver nitrate onto paper and then use the brush to spread as needed so you are not going back and forth dipping the brush in the cup. Or measure out the required quantity for one print into a separate cup and use that to brush out of.

As I mentioned earlier, you can just leave out the ammonia all together as straight silver nitrate would work just fine - unless your project demands that you replicate Talbot's original process precisely. And if you do make ammoniacal silver nitrate, make just enough for one sitting and not store it for future use.

Good luck!

:Niranjan.
 

NedL

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I think the post from Mike Ware should be taken very seriously. I've made a number of prints using "ammonio-nitrate" of silver and was always very careful not to let the solution evaporate or sit around at all and to wash everything with plenty of water immediately after use -- always making only what I would use right away. It is very problematic if there is any gelatin sizing on the paper ( I don't know anything about Canaletto paper.. no idea how it is sized ). It was a very popular way to sensitize salt prints in the early days. I've also made Mike Ware's agyrotype prints by making the silver oxide this way.
 
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lorien barker

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NedL... can you please expand on what you meant by 'very problematic if there is any gelatine sizing on the paper' please? The Canaletto paper I used I believe is 100% cotton rag. But I have just salted more paper... Adox baryta something to try, which has a gelatine coating... which worked excellently in getting an even coating.

I was double dipping my foam brush back and forth in the silver sol. and paper (not salt solution) so perhaps I was collecting salt and depositing back into the sol. hence precipitate. Either way... thank you all for your words of caution. Think ill take this one as a hit... and as you all say.. no ammonia, less solution, and pipette onto paper to stop contamination! Lesson learnt either way.

Cheers to all1
 

Donald Qualls

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I agree, the possibility of fulminating silver cannot be discounted. Ammoniacal silver nitrate solution used to be made for silvering mirrors (I'm familiar with it from reading about telescope making). There are recorded instances of old silvering solution (that had developed a precipitate after initial preparation) detonating when struck by sunlight.

Fortunately, amateur telescope makers have many avenues to get their mirrors vacuum coated with other metals than silver (which also last longer). Alt-process printers have fewer options, but one is not to ammoniate your silver nitrate solution...
 

NedL

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Yes, apologies for not being clear... the problem with gelatin is not a safety problem. In my experience, using ammonio-nitrate of silver as the sensitizer does not produce good results if there is gelatin sizing on the paper or if the salting solution was mixed with gelatin. Some of my friends who have tried this old fashioned way of making salt prints had the same experience. I don't know why it happens, but the ammonia-silver nitrate solution discolors the gelatin ( pinkish color, not nice looking ) and there are uneven areas. I think the ammonio-nitrate reacts with the gelatin somehow when it is being brushed on. If there was gelatin on the paper when you saw that mottling/disintegration problem, that might be the reason.

Some people "fume" their salted paper with ammonia just before printing it. The salted and sensitized paper is placed in the top of a closed box, printing side facing down, with some ammonia on the floor of the box so that the fumes reach the print. The paper is taken out of the box and exposed right away to make the print. It speeds up the printing a little and produces a deeper print-out... basically making the paper more sensitive. I've never heard anyone mention avoiding gelatin for this.

I think you will have better luck if you keep the silver nitrate sensitizer simple. Just silver nitrate and perhaps a little citric acid depending on whether your paper is staying white in the highlights or starting to fog.

Have fun, I hope you enjoy making the prints.
 
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nmp

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The problem with gelatin vs ammoinacal silver nitrate might have something to do with the isoelectric point of gelatin - which is the pH at which the solubility of gelatin is the lowest. For gelatin it is around 5. Solubility goes up on either side of the isoelectric point. I suspect ammoniacal silver nitrate is alkaline enough to be able to solubilize the gelatin, damaging the physical integrity of the coating as a result. Hardened gelatin might have less propensity to disintegrate, I would imagine.

:Niranjan.
 

NedL

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nmp said:
The problem with gelatin vs ammoinacal silver nitrate might have something to do with the isoelectric point of gelatin...
Click to expand...
Niranjan, that makes sense and fits with what I experienced. Pig skin gelatin has an alkaline ( pH 8 or 9 I think ) isoelectric point, so maybe that would have worked better....
 
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