Washing Ammoniacal Emulsions

[ThePhotoChemist]

Hey everyone!

In my spare time, I've started poking around with ammoniacal emulsions. So far I've tried a scaled-down version of Photo Engineer's SRAD formula, as well as Denise Ross's formula listed in her book.

I've only tried once with each so far, but I've had the same problem both times -- no matter how much I wash, I can't get the ammonia-smell out of the noodles! I've been very careful to not add too much ammonia when dissolving the silver nitrate (I've had a lot of practice at this step from silvering glass in the past). I'm very careful with my temperature setup, so I'm positive the emulsion never passed 45C.

Most recently with the SRAD recipe, I washed the noodles SUPER thoroughly (9x changes of water, about a gallon each, 10 minute soaks, with a small pump for recirculation). And after all that, the noodles STILL noticeably smelled like ammonia (though much fainter than before).

I remelted and added a bit of KBr for antifog, but it was getting late at that point, so I put it all back in the fridge. Today, when I took a little scoop and plopped it in some developer to see if it was fogged at this point, it mostly immediately changed to black -- except the part of the emulsion that would have been on top.

My guess is that the ammonia was easily able to gas off the top 1-2mm of the gelatin in the beaker, and so it did not cause fog. But deeper into the gelatin (which is to say, 99% of the rest of the batch), it hung around and fogged the heck out of it.

One thing I can think of - I didn't use ice to cool down the water while washing. So I wonder if the noodles just swelled too much, making the dispersion of the ammonia less efficient? Even so, I would think 9 10-minute washes would take care of it...

Thanks!

 

[RogerHyam]

Sorry I can't be of any help as I've been sticking with a pretty simple emulsion. I'm curios though as I'd like to get into ammoniacal or adding sensitisers. Where is Photo Engineer's SRAD formula? Is his stuff gathered together anywhere? Did he write a book?

Thanks

 

[ThePhotoChemist]

It's this thread right here!

 

[RogerHyam]

It's this thread right here!

Thanks - that looks simple enough. I might give it a go and see if I hit the same issues you have.

 

[ProfessorC1983]

A revised version of the ISO 40 SRAD formula appears in PE's book, "Photographic Emulsion Making, Testing and Coating" -- which is nearly impossible to get but I've finally succeeded in getting one of the few copies in library circulation via inter-library loan. The recipe is quite similar to the original posted in the thread above. Happy to discuss the differences via DM but don't want to post his copyrighted work on a public thread.

In general -- PE's advice was that the ammonia smell should be "almost" gone but not undetectable. I've actually scaled back my noodle wash of ammoniacal emulsions based on a note in his book that too much washing can add fog due to swelling, and have found this to be true in testing. Cutting back from 90 to 60 minutes, and only using distilled water for the final 2 changes (IOW I do 6x5min changes of filtered tap water, and 2x15min of distilled), has done wonders for my fog problem that had nearly caused me to abandon ammonia altogether. Yes I do still smell a faint trace of ammonia afterward.

Have you weighed the emulsion before and after washing to determine how much it is actually swelling? I've found roughly that if I get more than a 100% weight increase due to swell, the fog starts to become unmanageable even with added bromide.

 

[ThePhotoChemist]

A revised version of the ISO 40 SRAD formula appears in PE's book, "Photographic Emulsion Making, Testing and Coating" -- which is nearly impossible to get but I've finally succeeded in getting one of the few copies in library circulation via inter-library loan. The recipe is quite similar to the original posted in the thread above. Happy to discuss the differences via DM but don't want to post his copyrighted work on a public thread.

In general -- PE's advice was that the ammonia smell should be "almost" gone but not undetectable. I've actually scaled back my noodle wash of ammoniacal emulsions based on a note in his book that too much washing can add fog due to swelling, and have found this to be true in testing. Cutting back from 90 to 60 minutes, and only using distilled water for the final 2 changes (IOW I do 6x5min changes of filtered tap water, and 2x15min of distilled), has done wonders for my fog problem that had nearly caused me to abandon ammonia altogether. Yes I do still smell a faint trace of ammonia afterward.

Have you weighed the emulsion before and after washing to determine how much it is actually swelling? I've found roughly that if I get more than a 100% weight increase due to swell, the fog starts to become unmanageable even with added bromide.

I'd love a copy of the recipe, if you don't mind!

Thanks for the tips -- I definitely got a lot of swelling in my last batch. I was washing with RODI water, and I could tell it had taken on a lot during the washing. Probably well over 100%.

I will look into getting a filter and using tap water and seeing how that does!

I'm curious why this could be a mechanism for fog, whereas in other non-ammonia recipes it doesn't seem to be? My emulsion washer had a sequence bug the other day while I was washing a slower recipe, and it ended up swelling from 300mL to 700! But it doesn't show the tiniest bit of fog.

 

[ProfessorC1983]

I found a few of the quotes in Mowrey's book I was thinking of:

p. 60: "With all 3 of these washing methods, you must be careful not to overwash the emulsion. Too much washing reduces the excess salt to nearly zero and the emulsion keeps more poorly and has more of a tendency to fog with keeping."

p. 134: "It is good to have a slight positive test for Bromide ion in the wash water. Washing until there is no evident halide left can cause fog. The final washed, melted emulsion should be at about pH 6.5. This is optimum for the storage of any of these emulsions. It should have a slight amount of retained Bromide."

I have not been pH testing my emulsion post-wash, but will likely begin doing so as this seems to be the only semi-reliable method of determining wash completion. He also describes testing the wash water with a few drops of dilute AgNO3 (cloudy means remaining halide), but then mentions this test is inaccurate in the presence of ammonia.

The exact causal mechanism of low excess bromide leading to fog isn't explained by PE that I've seen, but I believe is covered in Wall's book; I'll track that down next. But I've certainly seen evidence of poor keeping when storing washed noodles for more than a few hours before finishing, in terms of both fog and pepper grain.

At a certain point I do begin to wonder if the extra speed is worth all these headaches... my plain-silver emulsions have been turning out quite beautifully and reliably despite being stuck around ISO 0.1

 

[ThePhotoChemist]

Well, when the emulsion is slopped on the back of an autochrome screen, it's even slower! My non-ammonia emulsions are hitting around 40 seconds in the sunlight, and I think all my friends are starting to get sick of holding still for so long! So I'm going to keep beating my head into the wall until I can get this working - eventually I'll break through from sheer stubbornness!

I think next time I take a stab at this (I think I have time tomorrow), I'm going to take a dropper and continue to take samples throughout the whole process. I'm about 95% sure it's occurring post-wash, but I'd like to be 100% sure!

I'll definitely be taking pH samples too. Mine very well could have been way out of range.

For washing style, I've been going off of PE's post here.

"John, I use distilled water. I overwash and then either use the emulsion right away or I add some bromide in. It would be useful to use about 0.03 g/l, which would bring the emulsion to about 100 mv. Nick and I both have had trouble with city water lately and filtration does not seem to work well."

From his other posts, it seems like you don't get insta-fog when you over-wash, but it will creep up quickly if you don't add some KBr back in. It seems to have gained me a bit of speed vs incomplete washing, but not all that much. Maybe that approach doesn't work when you've got ammonia present, though.

 

[ThePhotoChemist]

Here's an update:

After probably 8 runs over the last month (3 using Denise's TLF#2 and 5 using Ron's SRAD formula), I still have not yet successfully made an ammoniacal emulsion.

For my earlier washing problems: I found that 4x 15min soaks in icewater does the trick. I wasn't doing my due diligence when it came to wringing out the noodles. There isn't a noticeable ammonia smell after that.
However, I'm still having terrible trouble with fogging. I'm not just producing a lot of fog... my emulsions are completely fogged! There is no discernible image at all, and I have no idea why.

I took some samples throughout the process - starting with precipitation. For example, Denise's recipe calls for an addition of silver, 45 minutes of ripening, and then another addition of silver. With an eyedropper, I took samples after the initial silver addition, at 15 minutes, 30 minutes, 45 minutes, second silver addition, and a final sample at the 60 minute mark. When the samples are dried, I could see major darkening at the very first sample, getting worse throughout the ripening stage, and then another major darkening at the second silver addition.

It seems like the fog is all occurring right at the beginning! Though, since the samples are full of contaminants that are usually washed away during the noodle wash, I wasn't sure if these samples could be trusted.

Here's a little bit more information:

1. Dissolving the AgNO3 in ammonia. I am fairly certain I am not overdoing it with the ammonia addition. I heat the sample to 40C in a water bath with magnetic stirring, and add in the ammonia dropwise. When it starts to clear up I go very slowly, since it clears really quickly when you're near the end. The sample will smell very very faintly of ammonia, and is clear of any brown/black flecks.

2. Temperature control. I use a hotplate stirrer with temperature probe to control a waterbath, and then have a second digital thermometer monitoring the emulsion temperature. I have an insulator to keep the bottom of the emulsion beaker away from direct contact with the bottom of the waterbath/hotplate surface. The temperature never exceeds the value the recipe calls for by any more than 0.5C, and in the last few runs it was even under it a bit. I've cycled in a few different thermometers just to make sure the one I usually use isn't out of whack.

3. Water. I mostly use water from a RODI filter I have installed. In the last run I did, I was worried that there might be some contaminant from the city water that it's not catching, so I used distilled water from the store. Same results.

4. I made another run of Denise's AmBr emulsion last week, at the same time I was making ammoniacal emulsion. That one isn't fogged at all.

So that's where I'm at. I'm totally pulling my hair out!

Last thoughts: In a dream I had last night, I "solved" the issue after I realized that contact with metal (the metal thermometer probe, and a metal scoop I use to remove the stirbar from the silver solution) was causing the issue. Could that be the issue, or am I just losing it?

Thanks!

 

[Sparks n Fire]

what is the concentration of your ammonia?