Making my first emulsion now.

[Photo Engineer]

Well, it is nice to see people getting the chemicals they want.

VWR will not sell me a new reference electrode but some other companies will. I can get Silver Nitrate, but not Potassium Nitrate (because it is used to make bombs!), but you can get Nitrates most anywhere for fertilizer. Most hardware stores sell a dreadfully impure version of Potassium Nitrate for gardening use (it contains a lot of KCl). At the risk of being condemned, I'll tell you that some Silver salts are more explosive than you might imagine!

So, for those who say it is easy to get chemicals, I say go for it. But don't count on it being easy forever.

The Lab Depot is very good. It is a source I suggested in the workshop to my students, but I only get hardware from them. I also suggest Antec, www.kyantec.com for chemicals. I get my Erythrosine from them among other chemicals and hardware.

So, it is a mixed bag, but remember, I have watched this trend over time and seen the tightening of regulations. And, I might add a big YES to the quesiton "does this extend to prepackaged kits?". Some companies will not ship kits out. You can only pick them up at the store.

Look at UPS regulations. I cannot ship a developer. I don't have a license for shipping alkaline solutions. (Does that include Milk of Magnesia?). They have a large poster on the counter with 3 major prohibitions. Alkalis are one. Now, I can go across town and get a license from FedEx, and then take the open package to them for packing, pay an exorbitant fee, and have them ship it. UPS will reluctantly do the same from their main shipping depot here in the city.

PE

 

[Emulsion]

HRST, Very impressed by your results! Fantastic work.
PE, Your Millipore setup has me intrigued. I understand that you use it to concentrate and wash the emulsion. Is this correct? From what I have read the primary reason for concentrating the emulsion is to use it in a curtain coater. Is this also correct? Hope you can briefly explain.

Yours Intrigued,
Emulsion

 

[Photo Engineer]

Noodle washing of an emulsion causes it to absorb up to 10% or more water from the washing process itself, thereby diluting the emulsion. I have seen cases of 50% absorption which really dilutes your emulsion. This is true of some Ammonia emulsions that may be still a bit alkaline.

Therefore, UF (Ultrafiltration) is used on most all emulsions to remove unwanted salts at the end of the making process. This is regardless of final coating method.

Concentrated emulsions have been used in extrusion, slide and curtain coaters for years, as long as UF was available. It is just that it is more critical in slide or curtain coating but it is always nice to have an emulsion that is always 1 Kg per mole of silver. It makes calculations easier.

PE

 

[hrst]

Noodle washing of an emulsion causes it to absorb up to 10% or more water from the washing process itself, thereby diluting the emulsion. I have seen cases of 50% absorption which really dilutes your emulsion. This is true of some Ammonia emulsions that may be still a bit alkaline.

This was probably our biggest mistake first. We didn't neutralize ammonia before noodle washing and washed in 16...17C tap water for two hours. It may be about 50% absorption . This is probably why we had to adjust coating blade gap to 400 um instead of initial 200 um and our initial coatings looked good in red safelight before drying but didn't work at all.

Now we have a pH meter and we will refrigerate the wash water, and squeeze off excess water from noodles before re-melting. We also have a better noodelizer now, it makes thinner noodles, they should wash faster if I'm right.

Is there any reason why we cannot just lower the water volume in initial solution, say, 10%? It would then dilute to a proper value.

 

[Photo Engineer]

I wash in 4 deg C distilled water, and check the wash water as I pour it off for halide salts with a Silver Nitrate solution. When no Silver halide ppt. forms, the wash is done. I try to stop before that point by judging the mild cloudiness that forms as being the best point to stop.

My Ammonia makes (SRAD) are adjusted to pH 6.0 before washing. I use dilute Sulfuric Acid, as it is best in reducing swell and has no bad effects.

The vAg measurements will help this process become more accurate.

PE

 

[hrst]

Sulfuric acid contains sulfur but it has no effect. Okay. Then again, sodium thiosulfate contains sulfur and it is used as a source of sulfur for sulfur sensitization. Am I right that the difference lies in the fact that thiosulfate ion has two sulfur atoms whereas sulfate has only one?

 

[Photo Engineer]

No, it lies in the fact that Hypo decomposes to Ag2S on the surface of Silver Halides, but H2SO4 does not.

PE

 

[wildbillbugman]

I just received an order from VWR. Nothing dangerous unless your a 2-year old. But still,I bought as an individual with no business license of any kind.
Photo Engineer-Mabe they know who you are!
Bill

 

[Photo Engineer]

Bill;

I ordered a reference electrode from them 2 weeks ago. They took my order information and told me that in 4 days or less they would inform me if they could accept me as a customer without a business account (which is a real mess in NYS).

As of this date, they have not replied nor accepted my order.

PE

 

[totalamateur]

Why not take out a name in another state? In texas it's $10 and 1 form, unless you want a crop. or LLC. You don't have to do busines sin the state where you are liscensced.

 

[Photo Engineer]

Well, at this point it is probably more trouble than it is worth, but this still does not solve the problem of recieving some types of chemicals as the license must be gotten here in NYS to get the material shipped here. Also, many shippers require delivery to non-residential addresses. Once they start the delivery truck into a residential neighborhood, they would probably just turn around, IDK.

So, it is a thought, but probably impractical. I finally ordered the electrodes elsewhere from a small company that deals with this type of thing.

PE

 

[hrst]

Making new emulsion now.

Good evening!

We made a new emulsion now. It is really the second time that teaches you the most. The first time you don't understand what you are doing and just do, but the second time gives questions and you find new things. We are currently washing the emulsion. So, a few questions, if you don't mind! .

1. We made 1/5 of "A Real Formula". 26 g silver nitrate (0,153 mol silver), 22,82 g sodium bromide, A+B total 300 ml water at start. We needed about 25 ml 25% ammonia to get a clear solution, and that lead to the need of H2SO4 25% about 40-50 ml to get pH = 6.0. This lead to quite diluted emulsion again...

We used a plastic wrap over the beaker to reduce ammonia smell. Is this a mistake--does the formula expect a loss in water&ammonia due to evaporation in precipitation & digestion steps?

Is it normal to need this much ammonia and H2SO4 to neutralize it?

So, we started with 300 ml of water and needed total 48 g food-grade (pig) gelatin. Resulting amount was 420 ml of emulsion due to ammonia & H2SO4 dilution. This leads to 0,36 mol silver per liter. --- before wash. Is this too dilute?

2. We made an erythrosine emulsion. We added erythrosine 50 mg per mol of silver (7,65 mg) as 1% solution to bromide-iodide solution before adding silver nitrate. I'd expect that the finished ortho emulsion should be quite red/magenta. Just like sensitized enlarging papers are very magenta. However, our finished emulsion has only an orangish colour, definitely not red nor magenta. More like yellow that has a touch of red added. OTOH, the previous emulsion was light yellow so the difference is big. I attached a digital picture of unwashed noodle.

 

[Photo Engineer]

Here are some answers:

1. That is the right amount of ammonia by my experience, but it is 2x the amount of H2SO4. You see, at equal percentage, H2SO4 has twice the neutralizing power, and so you should have used about 10 ml of H2SO4. I leave the beaker open and allow ammonia to evaporate. It smells, but I accept that loss as helping in concentration. I weigh the emulsion at every step to keep track of the total bulk.

2. The actual color should be a mix of yellow and magenta, or a pale red. So, your emulsion looks to be a bit more yellow than mine.

And a comment. Pig gel used for food is much less viscous than Bone gelatin. It has maximum swell at pH 4.5 while Bone gelatin has max swell at about 9. These differences are making it difficult for me to judge just what is going on. Food grade Pig Gelatin has a Bloom Index as low as 75, while the gelatin I use is about 250 BI.

PE

 

[Photo Engineer]

Here is a clip still from the DVD showing my ortho emulsion after ISO Wash.

I use more PA gelatin than we did at EK, but it makes the ISO smoother for the average student, while leaving behind a few chunks that will not remelt.

PE

 

[hrst]

Thanks for the pic, yes, that's definitely much more red than ours. The color of ours is something between a non-sensitized emulsion and yours. So, we might expect less green sensitivity I guess.

Noodle washing was also quite a surprise. For 1,5 hours, the test solutions came out almost the same with much precipitate, then suddenly at 2 hours it was perfectly clean. I hope we didn't overwash it.

But, the most important thing.... This is indeed fun! Especially cleaning! Dead Link Removed

 

[Photo Engineer]

Yes, I hate washing dishes! I have a weeks mess to clean up right now from all of those vAg experiments.

But, your mess is typical of mine. Have fun.

PE

 

[wildbillbugman]

2. We made an erythrosine emulsion. We added erythrosine 50 mg per mol of silver (7,65 mg) as 1% solution to bromide-iodide solution before adding silver nitrate. I'd expect that the finished ortho emulsion should be quite red/magenta. Just like sensitized enlarging papers are very magenta. However, our finished emulsion has only an orangish colour, definitely not red nor magenta. More like yellow that has a touch of red added. OTOH, the previous emulsion was light yellow so the difference is big. I attached a digital picture of unwashed noodle.[/QUOTE]

-------------------------------------------------------------------------
I always use 100mg erythrosine per mole of AgNO3. My emulsions are distinctly pink,very much the color of strawberry ice cream.
Bill

 

[hrst]

Results

I tested our test coatings of this new emulsion.


Some notices:
1: FOG!!!! Last time there was none so this was not so nice surprise.
2: DMAX not so high. I think this is due to dilution. These new coatings are much thinner than last time but this is as diluted as before. Making thicker coatings would probably raise DMAX to same level as before but fog would raise too.
3: Speed seems to be about the same: about ISO 10.
4: Erythrosine was successful, it's sensitive to green! But green sensitivity is about a stop lower.
5: I made a test to add erythrosine (at about 10x higher level!) before coating and hold at 45C for 5-10 mins if it could work at some level. This showed no difference in green sensitivity, but otherwise the second coating was better, I would say perfect.
6: This emulsion, hardened with glyoxal, now sticks better to our (unsubbed) PET sheet. It survives the process almost well without over-careful handling.

And here it is, a scan made with Epson V700 flatbed film scanner:
Dead Link Removed . Digitally untouched . If you want a high-res image to evaluate grain etc, look at Dead Link Removed 600 dpi scan.

And finally, questions!

1: Fog!! Can it be due to overwashing? It's funny because the wash water sample at 1.5 hours showed much precipitate and at 2 hours it was 100% clean. Should have stopped at 1.5 hours?

2: Has anyone tried to add a very small amount of bromide (& iodide?) to emulsion to retard fogging? Maybe I should give it a try?

Next time a smaller batch. We have half a liter this foggy, "almost orthochromatic" emulsion now! .

 

[wildbillbugman]

I always add KBr after washing. 1% of original weight of KBr, to reduce fogging. KI at this point dose nothing. But this looks like one heck of alot of fog! I don't think that "over-washing" could cause fogging. But maybe the overwashing contributed to a thin emulsion.
Bill

 

[Photo Engineer]

Ok, you probably overwashed the emulsion, I think. You need to have some small amount of Bromide left. See the page on Jim Browning's emulsion on this. Wash to zero bromide then back off by adding a little bit before adding sulfur.

Remember too that sulfur + gold causes more fog than sulfur alone and that TAI (Tetra Aza Indene) can reduce Sulfur + gold fog by a great extent.

PE

 

[Kirk Keyes]

ANother thing to think about is your safelights. Make sure you have good safelights. You have your emulsion cooking with the safelights on most likely for a long time. It might be best to turn the safelight off except when you need it, especially once you add the erythrosine or when you get the mix right and you get faster film speeds.

 

[hrst]

Yeah, we have to test our safelights with this emulsion using loooong exposures. We use self-made LED safelights of 600-625 nm orangish-red leds. These have been especially good compared to filtered white-light sources. On this illumination level, I've seen no fog even for a hour or two exposure to multigrade enlarger paper. But, things have to be checked to be sure.

Next time we'll also refine our safelight practices. I'm going to build smaller, dimmer battery-powered safelights with on-off switch and use them just when needed. But, I don't believe that the problem would be here since these safelights are quite good and there are no filters that would fade. They just don't produce any shorter wavelengths than orange.

I'll test adding some bromide to this emulsion.

Would it be a good idea to add some bromide to wash water next time? First half an hour with distilled water and then with DW with some bromide in it. It would ensure that at least all bromide cannot be washed away.

 

[Photo Engineer]

Add bromide in the quantity and at levels as suggested in the article by Jim Browning at his web site. The final vAg should not go above about +100 mv or you risk fog.

I'll calculate the salt quantity later and post it here.

PE

 

[hrst]

I tried to add 12 mg of NaBr per 30 ml of emulsion. (Jim Browning seems to suggest 6 mg KBr per 30 ml of emulsion if I calculated it right). I dried it quickly with a hairdryer and emulsion loosened, but, the results is: the fog stays. There may be a little less or may not, I have to make a better comparison with the previous ones. It may be a little faster, though, with the same fog. Have to check it.

And it may be too late now to add the salts because it has been in noodles for two days. Or what do you think?

 

[hrst]

Can someone explain or give some pointers why exactly overwashing causes fog? I understand that fogging of a halide crystal can be caused by a single metallic silver atom in the crystal that works as a developing center. Does the little amount of salts prevent this or how it works?