# Silver Recovery from X-Ray Film



## RikkiRicardo (Apr 21, 2012)

Hi has anyone tried Silver Recovery from X-Ray film with Alkaline Protease strain Bacillus subtilis
there is a firm in the US that sells this sure there are other companies Bio-Cat INC
here is a link but there is a lot more info on this.if you search.I would be trying this but here in Romania it is very hard to get this stuff

http://www.ku.edu.np/kuset/vol6_no1/7_Seeta.pdf


----------



## Palladium (Apr 21, 2012)

Don't know anything about it but here's a good read on film. http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=11047&hilit=silver+xray+sodium+hydroxide


----------



## goldsilverpro (Apr 21, 2012)

I used that or some other enzyme for stripping film in about a 300 gal tank. This process works great for rare earth or litho but not for dryview film. It was quite popular when it first came out as a proprietary product. The problem was that it made the building constantly smell like a sewer. Most people switched back to caustic soda even though the enzyme was safer. I know I did. It really stunk.


----------



## RikkiRicardo (Apr 21, 2012)

GSP Thanks for the info
Now what is the difference dryview film and x-ray film also what do you mean by rare earth?
Also i was thinking of making a vessel with a ventilation that would get rid of the smell and with a motion so that the film would be moving around
in the vessel also we would add low heat what do you think of this.
I like the part that it is safer to use.

RikkiRicardo


----------



## goldsilverpro (Apr 21, 2012)

RikkiRicardo said:


> GSP Thanks for the info
> Now what is the difference dryview film and x-ray film also what do you mean by rare earth?
> Also i was thinking of making a vessel with a ventilation that would get rid of the smell and with a motion so that the film would be moving around
> in the vessel also we would add low heat what do you think of this.
> ...



If you check this chart, rare earth came out in 1984 and it soon became the standard x-ray film. It required wet chemistry to develop it. In 1996, Kodak came out with a new product called Dryview. It looks exactly like the rare earth film, when developed, but it is developed by heat rather than chemistry. By 2005 in the US, about 1/2 of the x-ray film used was dryview. The problem is that it often comes mixed together and it is almost impossible to sort. Also, some brands or varieties of it have much less silver than rare earth. If you processed it all together with enzyme, only the rare earth film would strip. Even the caustic won't do a very good job of stripping the dryview unless the solution is quite hot. To test for dryview, hold a cigarette lighter about a 1 cm under a clear (no black) area of the film. Within a second or two, you will have a black spot if it is dryview. However, please note that any type film will burn and turn dark if you hold a flame under it long enough. This needs a little practice with both types to be able to tell the difference.

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=34&t=3735&p=50819hilit=rare+earth+litho#p50819

It may be different in Romania and maybe the dryview isn't used there as much. If you have a choice, buy "wet" film and not "dry" film. Sometimes in the trade, those are the terms used for the 2 different types.

I have always wondered if the enzyme used for septic tanks might work for rare earth. The common one in the US is called Rid-X. Make up a 30 - 50 gpl solution of baking soda (sodium bicarbonate) and heat it to about 40-45C. Add some Rid-X (or, whatever you have in Romania) and hopefully it will dissolve. I can't tell you how much to add but it will probably be just a very small amount. The proprietary film stripping product I used was in liquid form and, for a 300 gal tank, I only had to add 400ml each day. Worth a try with the Rid-X. If it works, it will certainly be cheaper than the proprietary enzyme. About 23 years ago, I was paying $100/gallon for it.

When using enzyme, the smell is not terrific, but you do get used to it if you don't think about it. The odor won't hurt you but it is ever-present, sometimes faint and sometimes strong.

Like caustic, you can use the same solution over and over and over. Let the sludge settle, then siphon off the solution and re-use it. If a little of the solids come over in the siphon, don't worry about it. It's not going anywhere and you'll get it all eventually. You can also re-use the solution from when you filter the sludge. The purpose of the sodium bicarbonate is to buffer the solution at about a pH of 8.5. It isn't used up in the reaction and the only time you have to add any (rare) is from losses from drag-out on the film. The enzyme acts as a catalyst and isn't consumed, at least during the day when operating. When it sits overnight, however, it decomposes and a full shot must be added each morning before you start stripping. At least, that's how the enzyme I was using worked. Don't ask me why.

If you get into this in a big way, I would use caustic instead of an enzyme. That is, unless you buy can 100% rare earth and no dryview and can live with the smell. The safety of the enzyme is a plus, though, but anything is safe if you know what you're doing and have the right equipment.


----------



## cwhardesty (May 5, 2012)

GSP,
from what i gather, you are the one to talk to about silver recovery from x-ray film.
can you give me any suggestions for recovering silver from dryview film? 

i have tried strippng using NaOH at 75 degrees C and got everything stripped from the plastic base, but never got further than that. the plastic base was clean, but the black layer remained together in pieces. not sure if this was the mylar or the gelatine/silver layer??? i tried 95 degrees C and stirring at 1500 rpm for a few hours, but never got any results. i also tried removing the black plastic pieces and stirring with no luck. my understanding was that at that temp and stirring, the silver would come out of solution. i am a novice if you have not gathered that yet and i am sure i am doing something very basic incorrectly.

i have also tried oxalic acid, but never got it to dissolve the dryview. this method did work great for wet film, but not on the dryview.

any suggestions would be greatly appreciated. 

And does your book cover these topics???? Can i pick it up on ebay? I would love to have it!!!!

Thanks,

Chris


----------



## goldsilverpro (May 5, 2012)

cwhardesty said:


> GSP,
> from what i gather, you are the one to talk to about silver recovery from x-ray film.
> can you give me any suggestions for recovering silver from dryview film?
> 
> ...


What strength NaOH are you using? Is the film chopped up?

My book does not cover film processing, at least in detail.


----------



## cwhardesty (May 5, 2012)

GSP,

Thanks for the quick response! The NaOH was 1 Mol (or about 4.5% by weight). After a an hour or at 95C about half of the film was stripped, meaning most of the base plastic pieces were totally clear. the pieces were about 1inch by 1inch. i had to manually separate the clear base film pieces from the black plastic that was coming off the film, as the film pieces stuck together trapping some of the black stuff. these black plastic pieces were floppy when in the heated NaOH, but would turn almost hard and plastic if removed. i think that is the mylar layer added to dryview, does that sound correct?

i am using a heated magnetic stirrer to process this in very small batches currently, at least until i get the science down. i had to remove the base film pieces so my stirrer would work. this was a time consuming headache. i was left with a yellowish/orange liquid that still contained the black floppy plastic pieces. i heated this for an hour and stirred at 1500 rpm with no sign of any silver particles.

i also tried to raise the concentration of the NaOH solution to 2 Mol, heated and stirred at 1500 rpm for 2 hours. The only thing i saw (and this may be key?) is some white slimmy substance floating in the liquid. i filtered by pouring the liquid through several layers of paper towels. after a day or so the white substance dried into a white powder. Not sure exactly what that is, could it be some form of silver?

The article i was using: (http://journals.tubitak.gov.tr/chem/issues/kim-03-27-1/kim-27-1-17-0109-1.pdf) seemed to indicate that that i would see silver particles.

i have not tried this method with wet film yet. And FYI, i scoped out the TOC from your book and was very impressed with the content. i will be getting a copy this up ASAP!

Thanks,

Chris


----------



## goldsilverpro (May 7, 2012)

Dryview is very difficult to strip, compared with the standard "wet" rare earth film. The emulsion is different and the black layer containing the silver tends to come off as a sheet rather than break up into fine particles, like that on normal "wet" film does. It almost has to be tumbled constantly so that the black silver layer will come off mechanically - you need movement - essentially the black rubs off with the mixing. Ours was chopped to about 3/8"-1/2" and was run in a large cement mixer for an hour at 200F. The NaOH concentration was about 4%.


----------



## sena (May 7, 2012)

Is heating necessary ? i never heated , i used 2kgs Naoh for 100kg of Industrial flims, leave it for a night . i think may be due to the climatic condition in India.


----------



## goldsilverpro (May 7, 2012)

sena said:


> Is heating necessary ? i never heated , i used 2kgs Naoh for 100kg of Industrial flims, leave it for a night . i think may be due to the climatic condition in India.



Were you stripping Dryview? Doesn't sound like it. All industrial x-ray film I have seen is standard silver halide film, which strips fairly easily in caustic. Dryview is a totally different thing. The emulsion is different and the silver is there as silver behenate (I think) and not silver halide.


----------



## sena (May 7, 2012)

goldsilverpro said:


> sena said:
> 
> 
> > Is heating necessary ? i never heated , i used 2kgs Naoh for 100kg of Industrial flims, leave it for a night . i think may be due to the climatic condition in India.
> ...


Thanks chief.


----------



## cwhardesty (May 7, 2012)

goldsilverpro said:


> Dryview is very difficult to strip, compared with the standard "wet" rare earth film. The emulsion is different and the black layer containing the silver tends to come off as a sheet rather than break up into fine particles, like that on normal "wet" film does. It almost has to be tumbled constantly so that the black silver layer will come off mechanically - you need movement - essentially the black rubs off with the mixing. Ours was chopped to about 3/8"-1/2" and was run in a large cement mixer for an hour at 200F. The NaOH concentration was about 4%.



Thank you for your suggestions GSP! That is very helpful!

Chris


----------



## cwhardesty (May 8, 2012)

goldsilverpro said:


> Dryview is very difficult to strip, compared with the standard "wet" rare earth film. The emulsion is different and the black layer containing the silver tends to come off as a sheet rather than break up into fine particles, like that on normal "wet" film does. It almost has to be tumbled constantly so that the black silver layer will come off mechanically - you need movement - essentially the black rubs off with the mixing. Ours was chopped to about 3/8"-1/2" and was run in a large cement mixer for an hour at 200F. The NaOH concentration was about 4%.



GSP, did the black silver layer every disolve fully for you? i did get it seperated with a bit of work, but it just remained in 1inch large sheets.

how did you actually seperate the silver? my article said that heat and stirring would make the silver particles fall out? suggestions?

thanks,

FYI, i just sent you $35 for a digital copy of your book via paypal. transaction #8BT6477849460590S. My email is [email protected]
Thanks again!

Chris Hardesty


----------



## sena (May 9, 2012)

Is there any difference between the composition of silver , both are the industrial x ray ( silver halide flim) ,there is colour difference any guess? 

Thanks 
Sena


----------



## goldsilverpro (May 9, 2012)

sena said:


> Is there any difference between the composition of silver , both are the industrial x ray ( silver halide flim) ,there is colour difference any guess?
> 
> Thanks
> Sena



No. I saw so many different colors of film, I stopped worrying about it. It could have to do with different manufacturers or, more likely, different amount of exposure to light. All industrial x-ray I've ever seen was silver halide film.


----------



## kurt (May 12, 2012)

Ok – I have access to a barrel full of X-ray film. The guy that has it gave me a hand full of it to play with (it’s only about ¾ lb) I have tested it with Clorox & it striped the black off so it is the silver halide type.

I have read this thread as well as the “view topic” thread link provided by Palladium. The part that is going over my head is the 4% sodium hydroxide. How much (dry form) sodium hydroxide do I mix with a gallon of water to get my 4% sodium hydroxide solution. I have no idea on how to figure out dry weight to wet volume to come up with 4% concentration. 

Kurt


----------



## Geo (May 12, 2012)

some generic brands of household bleach is 4% and others are 5%. you just have to check labels.


----------



## Oz (May 12, 2012)

Geo, sodium hydroxide is not “household bleach”. Household bleach is sodium hypochlorite.

To try to answer the question though, typically it is done by weight. The mass of NaOH being 4% of the total mass after water has been added.

You are in the right thread, but I would suggest that you wait for goldsilverpro to reply here. When it comes to any type of film I know of no one else here with greater experience.


----------



## Geo (May 12, 2012)

thats what i get for reading in my sleep.  i think ill go back to bed now, sorry.


----------



## kurt (May 12, 2012)

That’s OK Geo – I have been known to do the same thing

Oz – thanks for the reply – from all the reading I have done on this we might need to do a coin toss to see who the winner is between Chris & Manual

Anyway – that’s where I am at a loss (I am not very good at math) we have weight, volume, &/or mass – all of those things are different things. So it’s 4% NaOH to what? And how do I calculate that?

My NaOH is dry form. 

Kurt


----------



## goldsilverpro (May 12, 2012)

1000 x .04 = 40g/l


----------



## cwhardesty (May 12, 2012)

goldsilverpro said:


> Dryview is very difficult to strip, compared with the standard "wet" rare earth film. The emulsion is different and the black layer containing the silver tends to come off as a sheet rather than break up into fine particles, like that on normal "wet" film does. It almost has to be tumbled constantly so that the black silver layer will come off mechanically - you need movement - essentially the black rubs off with the mixing. Ours was chopped to about 3/8"-1/2" and was run in a large cement mixer for an hour at 200F. The NaOH concentration was about 4%.



GSP,
reading your book and the excerpts from the forums. Wow, great stuff! I have already learned so much and i am just scratching the surface. Thank you for putting that together! It really is timeless.

a question about the above quote. how did you physically separate the stripped, clear film base pieces from everything else. The small pieces definitely seem to strip easier, but i just end up having to fish all those small pieces out to get at the good stuff. Any suggestions?

Thanks,
Chris


----------



## goldsilverpro (May 12, 2012)

It was augered out of a cement mixer and spray rinsed, every 18", while moving through an auger about 40' long.


----------



## kurt (May 13, 2012)

Daaa  Thanks GSP --- Can I blame it on the fact that I was a HAADD (hyper active attention deficit disorder) kid way back before they had a name for it. :lol: 

I gotta stop thinking in U.S. measurement & start thinking in metric :!: 

As they say - it's hard to teach an old dog new tricks
- & I am living proof :lol: 
Kurt


----------

