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Potassium Bromide replacement / removal

glpozza

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I intent to mix my first batch of wet plate emulsion, but just discovered Potassium Bromide is forbiden were I live. Even worst, I believe every bromide requires an authorization from federal police. Could it be replaced by any other anti fog agent? Assuming I skip it and just use gelatine and silver nitrate, would the result be highly unaceptable? I know the short answer would be "just try it", but since silver nitrate is really expensive, I need your thoughts and experience.
Thank you.
 
The Potassium Bromide is much more than an anti fog agent. It supplies the halide to make the light sensitive silver halide.

You ask "Assuming I skip it and just use gelatine and silver nitrate, would the result be highly unaceptable? " and the answer is YES
 
Hi,

Are you meaning wet plate or dry plate? Different processes. Different chemicals. Wet plate doesn't use gelatin (at least any variation I'm aware of.)
If you're talking dry plate, sodium chloride would work as the halide, but you would get a very slow emulsion. Do some research on photographic halides and compare what you find against what you are able to buy.
With wet plate, what are the halides used besides iodide?
d
 
You are confusing the use of a restrainer (antifoggant) with the use of potassium bromide to actually create an emulsion. You must have a soluble bromide. You don't say where you live which might be helpful in naming sources.

For a wet plate (collodian) emulsion you need a bromide that is soluble in ether. Cadmium bromide is usually suggested. This can be a problem since cadmium salts are very toxic. Substituting sodium chloride will not work because it is not soluble in the ether-alcohol solvent.
 
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My bad! It was suposed to say DRY plate.
I live in Brazil, and several chemicals are restricted, many from pure ignorance, like collodium. Import (from BH or B&S) would be a bigger problem. I'm not sure if it is implicit, but its suposed to be used inside a LF camera. So, when you say I would get a slow emulsion using salt (sodium chloride), you are talking about something that would still be usable in this condition, and not something like a 45 minute exposure in a bright day, right?
 
No where near that bad . In good, strong Brazilian sunlight, at f/8, it shouldn't be more than 5 min, probably less depending on the subject matter. If you do this, I hope you report back with details!
 
Well... It's not bad at all.
So, 12% AgNO3 slowly added to a 2% NaCl and 10% gelatin (modified salted paper recipe) sounds like a good starting point?
Also, I don`t seem to find references of the emulsion width. Based on my carbon printing experience, I would guess around 0.25mm.
Am I way off?
 
dwross said:
In good, strong Brazilian sunlight, at f/8, it shouldn't be more than 5 min,
Click to expand...

But then only 3 stops down we're in the 40 minute range surely?
 
glpozza,

The best I can recommend is to jump off from this recipe:

http://thelightfarm.com/cgi-bin/htmltutgen.py?content=08Mar2013

Substitute 3 g of sodium chloride for the potassium bromide and leave out the KI. All the info you need to go from raw to cooked and in a camera is in the preceding pages.

The emulsion goes down at about .25 mm, but dries to considerably thinner.

Hope you have fun!
d
 
Thank you. I'll get the chemicals and report back with the results. It may take some time.
What is the role of the potassium iodide? Would it also increase the film speed?
 
Have you checked up on availability of Potassium Iodide? It would be very strange if you can get that but not be able to get KBr.

I tried to get some here in Aus, from a local chemical shop I have to fill in an End User Declaration saying that I won't use it to make drugs. KBr I can just buy. But Aus retail is expensive so I went to ebay.
I ended up buying all my chems from a guy in Poland off ebay. KBr made it to my letterbox last week with a note from Australian Customs saying "we opened it to inspect but didn't take anything".
The KI hasn't made it here yet, I suspect I'm going to get a letter next week saying "we confiscated it" (it's happened before with some jewellery I bought that they thought were weapons, seriously).
The AgNO3 is in the same box as the KI, so I hope they at least let that through. AgNO3 locally is triple the price of ebay.
 
A few years ago, potassium bromide were used in bakery shops to increase the size and reduce the weight of some products. As a result it got rated restricted, so I need an especial authorization (meaning a trip to bureaucracy hell). I found potassium iodide, and it seems to be easy to purchase.

Edit: And I just remembered that household salt has a little potassium iodide in it.
 
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IF you are willing to experiment a bit, you may be able to find Sodium Bromide at a local retail outlet the sells chemicals for maintaining swimming pools/spas/hot tubs. It is used instead of Chlorine in many spas/hot tubs as it does not smell as harsh as chlorine and is therefore easier on the users. A quick look online find the first US e-seller having it for US$12 + shipping for 1 pound (~475grams) in the granular state at 99% sodium bromide.
 
Potassium bromide was used for many years as a mild sedative. It was an ingredient in the OTC headache remedy Bromo Seltzer. I believe that potassium bromide is still used by veterinarians.
 
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No bromide is alowed here, not even under a comercial name. I'll buy the AgNo3 and use table salt (before it is forbbiden here).
 
Are you quite sure that that it is Potassium bromide that is banned and not Potassium bromate ?

They are quite different substances
 
Well that's very kind of you but I just googled "bromide brazil" and got hits back about bromate

It seems it (bromate) was indeed used as a flour "improver" in many many countries but is now widely banned (including in Brazil) as there is evidence for carcinogenic effects in rodents.

Not sure why you arelinking to an australian site btw - OP is in Brzil
 
Yes, you are right. I mixed the names. In portuguese it's even worst, as only one letter changes. Nevertheless, either brometo and bromato need a special authorization. The australian site is amazing, but I can't import raw chemicals.
 
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Apologies. I don't remember where I read that Brazil and a couple of other South American countries could import easily and inexpensively from Australia.

Don't use table salt. If you can't get photo quality sodium chloride, use pure sea salt.
 
It would be great, but sadly, to import anything to Brazil is getting harder everyday. The increasing taxes, the really bad postal service and the legal restrictions are the main dificulty to every brazilian person interested in alternative processes that I know. On the bright side, I had to learn how to make my own carbon tissue, developer, and soon an alternative for the lack of bromide.
 
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