PDA

View Full Version : Some thoughts on the use and management of salts in making Silver Halides.



Pages : 1 [2] 3 4

RalphLambrecht
10-20-2013, 10:34 AM
just imaginhow hard and costly itwill be to get all this knowledge and technology back once it is gone. the effort of reentry into a 'lost' technology is gigsntic. 'too bad' just doesn't cut it anymore.

Rafal Lukawiecki
10-20-2013, 01:05 PM
just imaginhow hard and costly itwill be to get all this knowledge and technology back once it is gone. the effort of reentry into a 'lost' technology is gigsntic. 'too bad' just doesn't cut it anymore.

That's the gist of what I heard Neil Armstrong say about the technology and the know-how of going to the Moon. He remarked, a few years ago only, that we have lost that ability.

Preserving knowledge, especially that which is unwritten, or is passed on as experience, or remains locked up in corporate drawers to be forgotten lest be shared, seems much more important than society cares for. Many thanks to Ron, and others, for sharing it, and the Ralphs of this world for neatly tabulating it in hugely informative books. Hats off to you.

kb3lms
10-22-2013, 08:14 PM
Ah... so that was a method of "employee discipline" at EK?

As an aside, there is an electrical engineer that I know that once worked at an Australian colliery on a belt system that moves 24 tons of coal per minute. There was a bug in the software that caused one section of belt to stop dead while the previous section kept running. Due to the mass of the coal it takes the belt a while to stop.

The miners handed the engineer a shovel and went home.

kb3lms
10-22-2013, 08:21 PM
Ron, this is very interesting. Thank you for your posting.

We once exchanged some messages about using Ammonium Thiocyanate as a solvent in a double run emusion. I had found it in a Kodak patent from 1967. Is that method used at all for production purposes?

-- Jason

Photo Engineer
10-22-2013, 10:27 PM
Jason, NH4SCN is used as both a solvent and as a source of Sulfur in sensitization. It rather depends on level and time of addition to get the desired effect. The problem is that SCN is hard to shut off if used as a solvent and so you can over Digest the emulsion leading to fog.

In some cases, it is (or was) removed by Ultrafiltration which is rather messy for home darkrooms.

PE

kb3lms
10-23-2013, 05:55 PM
So, a door is opened to a new mystery. :D Good!

Time to check understanding:

Everything I have made so far has used a full ammonia digest, meaning all the silver has been converted with ammonia before precipitation. (Precipitation being the combining of the silver with the halide to create, for example, silver bromide.) But from my reading and studying, it seems ammonia digest is NOT the way forward to "better" emulsions. (In my case better means more speed with good contrast. I can get to ISO 50, but I want to get ISO 100 give or take a few "isos".) Everything written so far in all these postings seems to confirm that.

What I gather, then, from this and other postings and books is that a solvent is not actually necessary. And many, or most, emulsions are made without a solvent.

Ammonia can be used to "homogenize" the crystal types and get you a good (better?) but not ideal dispersion. (Dispersion in this case meaning distribution of sizes and crystal types) The longer the solvent is active, the narrower the range of sizes you get (because the ammonia dissolved the smaller ones and they attach to or form larger crystals) which makes the emulsion more monodisperse, which increases contrast. And you might get a speed increase because you get larger crystals. If you keep this going long enough you get fog.

But the crystals all become rounded and eventually you wind up with round pebble grains, or klunkers I think you once called them PE. So you would lose any advantage of making cubes, octahedra or t-grains because the ammonia solvent would round them all down to pebbles. So, basically, using ammonia you lose the possibility of controlling crystal habit.

To summarize, an ammonia solvent makes it easier to get a decently working emulsion but not something you'd actually use in production work. It's a short-cut, but you give up control to get there.

Am I on the right track?

Photo Engineer
10-23-2013, 07:31 PM
Jason, a true Ammonia digest had been used for years in making high speed (ISO 100 or thereabouts) emulsions but that is not done currently. The reasons are fog, non-uniformity from batch to batch and the odor. Today, the same (or similar) results are obtained with double run emulsions.

Now, while DR is important, don't dismiss the Ammonia digest. It will work for you and at less cost (but more odor). The only Ammonia make that I don't use and don't recommend is one using NH4X (Ammonium Halide salts) as they have many additional problems and do not work as well.

I will say that the straight lines and long curves of modern high speed films are obtained by DR makes with vAg control, but then again, a lot of speed comes from the Sulfur+Gold sensitization as well. Without that latter step, you have nothing much.

PE

Hexavalent
10-23-2013, 07:39 PM
Several patents refer to the use of thioethers (some being rather exotic crown structures) as "modifying the crystal habit" or "facilitating crystal growth". Would these be considered "solvents" of a type, or something more akin to "catalysts".

Just for fun, I looked up the pricing on a couple crown ethers and they are mighty pricey little beasts!

Photo Engineer
10-23-2013, 11:02 PM
Ian, they are very expensive and once present, hard to turn off. They also cause a lot of fog if not handled properly. They are removed by diafiltration after they have done their work.

PE

dwross
10-24-2013, 12:55 PM
The only Ammonia make that I don't use and don't recommend is one using NH4X (Ammonium Halide salts) as they have many additional problems and do not work as well.

PE


Must resist posting...
Must resist posting..
Dang. Failed. :)

http://www.thelightfarm.com/Map/Index/PaulDeAngelis1/WholePlateHomemade.htm

http://thelightfarm.com/cgi-bin/htmltutgen.py?content=15Jun2013
http://thelightfarm.com/cgi-bin/htmltutgen.py?content=31Aug2013
http://thelightfarm.com/cgi-bin/htmltutgen.py?content=02Sep2013
http://thelightfarm.com/cgi-bin/htmltutgen.py?content=07Sep2013

Photo Engineer
10-24-2013, 04:14 PM
Here we go again. Read my OP. I said much the same thing there.

And, just because it was used 100 years ago does not mean that it is good, better or best. It NH4X salts were not in common use for manufacturing or hobby purposes for nearly 75 years due to lack of any overwhelming advantage!

PE

dwross
10-24-2013, 06:14 PM
75 years. Yup. That's just about perfect :). Kodak materials were in their glory. In 1938, Katherine Hepburn and Cary Grant were "Bring Up Baby". One of my favorite movies, "It Happened One Night", was already four years old. Lovely films, both. My bridge across the Yaquina Bay was two years old. So was Hoover Dam. And the Golden Gate Bridge. The 1930's were an economic challenge for many people, but as far as technology, and art -- I'm proud to have my work harken back to those times.

Jim Noel
10-24-2013, 06:29 PM
Thanks for taking the time to post this. Your first paragraphs answered a question I have pondered for too many years.

Jim

Prof_Pixel
10-24-2013, 06:34 PM
That sounds like non sequitur reasoning to me. Just because things were done someway 75 years ago doesn't mean we should do them that way today; 75 years ago, cars used leaded gas and had tube tires. Who wants those things today.

dwross
10-24-2013, 07:00 PM
Well, I guess your attitude is consistent for a guy who has the brass to use "Prof Pixel" as a username on APUG.

You may want to consider being a bit less dogmatic when you're around Mark Osterman. His bread and butter, and that of George Eastman House, is all about preserving the old and historical. Some people actually want to do just that. Perhaps you could leave us to our personal tastes and goals.

http://www.thelightfarm.com/Map/Books/Osterman/MapTopic.htm

Photo Engineer
10-24-2013, 07:30 PM
Mark's emulsion does not use any Ammonium Halide salts.

Denise, as stated in the OP, you can make Phosphorous by distilling rotted horse urine from a bed of sand. That is not done today for a number of obvious reasons, but the method works even today.

You can make emulsions with NH4X salts, but it is not necessary. It adds nothing to your work except the label "exotic" and it takes up space on your lab shelves and in your refrigerator. Yes, you can stock all 7 major Halide salts, but I can make do with just 3. It saves money as well.

So, why use it? IDK. None of my co-workers used it. As stated above, they did use (NH4)2SO4 and NH4OH for making emulsions and to much better effect. See those electron micrographs again!!

PE

dwross
10-24-2013, 08:01 PM
OK. One more try. Any more and I'll have to go find a giff about beating a dead horse.

You ask "why?". It is a far more beautiful emulsion than the identical one with KBr (to me, and who else matters?)

It allows the use of much more vigorous developers, so it is effectively faster.

I made a full ammoniacal emulsion today. The one that will allow me to shoot my 120 rangefinder handheld at a festival this weekend. But, you see, I have excellent ventilation. It wouldn't be so simple if I didn't. Many people are unable to make ammoniacal emulsions. That doesn't make them second class citizens. They should have options. I would never think of telling people they shouldn't be making your emulsions. Actually, I'm not sure exactly what "your" emulsions are. Never see pictures.

I only stock two bromides. Potassium and ammonium. Does that mean I "win" that particular contest?

I'm sure you'll come back again, swinging from a different corner of your box, but now it's my turn to ask "why?" I'll leave your answer unchallenged.

StoneNYC
10-24-2013, 08:34 PM
OK. One more try. Any more and I'll have to go find a giff about beating a dead horse.

You ask "why?". It is a far more beautiful emulsion than the identical one with KBr (to me, and who else matters?)

It allows the use of much more vigorous developers, so it is effectively faster.

I made a full ammoniacal emulsion today. The one that will allow me to shoot my 120 rangefinder handheld at a festival this weekend. But, you see, I have excellent ventilation. It wouldn't be so simple if I didn't. Many people are unable to make ammoniacal emulsions. That doesn't make them second class citizens. They should have options. I would never think of telling people they shouldn't be making your emulsions. Actually, I'm not sure exactly what "your" emulsions are. Never see pictures.

I only stock two bromides. Potassium and ammonium. Does that mean I "win" that particular contest?

I'm sure you'll come back again, swinging from a different corner of your box, but now it's my turn to ask "why?" I'll leave your answer unchallenged.

I've been following this thread out of curiosity since PE is "dropping the knowledge" but it's still a little far advance for me most the time, but I have a simpleton question.

You said it allows for more vigorous agitation, but wouldn't that also make for really grainy images? I know that's not really the question here but I guess it seems sort of counterproductive to make an emulsion that you can only make fast by making it severely grainy. unless you are specifically going for that look.

Please forgive me if I'm totally confused here.


Sent w/ iPhone using Tapatalk

dwross
10-24-2013, 08:47 PM
Hi Stone,

The fact that you are totally confused is sad beyond expression. It's certainly not your fault. Making emulsions (at the home darkroom level) is simpler than baking a cake. It is nearly tragic that it is not allowed to be simple here.

I didn't mean vigorous agitation. Rather, more vigorous developer formulas. The best I can respond is to ask you to read three short pages, starting here: http://thelightfarm.com/cgi-bin/htmltutgen.py?content=15Jun2013

Photo Engineer
10-24-2013, 09:07 PM
Denise, there are people here that make high speed emulsions with absolutely no Ammonia whatsoever either. So, just about anything is possible. It is what you must do vs what is optional that is being described (and tested) here in this thread.

It is certainly easy to make an emulsion. I use NaBr, NaCl and KI as my 3 salts. I use NH4OH as my source of Ammonia if desired. I get good speed and tone. You have seen my prints and plates personally snf do have my students. So, if what you do makes you happy, then do it. I do what seems to make my students happy and it also makes me happy.

Best wishes.

PE