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Photo Engineer
10-24-2009, 05:40 PM
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
10-25-2009, 02:23 PM
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
10-25-2009, 03:46 PM
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
10-25-2009, 04:00 PM
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
10-25-2009, 04:32 PM
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! :D http://sorsa-tv.ath.cx/~antalh/en_haluu_siivota.jpg

Photo Engineer
10-25-2009, 04:50 PM
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
10-25-2009, 04:58 PM
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]

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

hrst
10-26-2009, 09:12 PM
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:
http://sorsa-tv.ath.cx/~antalh/own_yeah.jpg . Digitally untouched :). If you want a high-res image to evaluate grain etc, look at http://sorsa-tv.ath.cx/~antalh/own_yeah_big.jpg 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! :D.

wildbillbugman
10-26-2009, 10:14 PM
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
10-26-2009, 10:35 PM
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
10-26-2009, 11:38 PM
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
10-27-2009, 04:15 AM
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
10-27-2009, 09:29 AM
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
10-27-2009, 12:24 PM
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
10-27-2009, 12:27 PM
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?

Photo Engineer
10-27-2009, 01:02 PM
Once formed by overwashing, over ripening, over digestion or over finishing, fog is difficult to remove. In the case of overwashing fog is caused by the high vAg which produces or allows production of more Silver metal which can act as a fog site. The KBr must be added at the time of washing when the endpoint is reached. The others produce fog by forming more Silver sites on grains through too much of a good thing!

Ideally to stay between +100 and +50 mv you will need about 0.029 and 0.192 g/liter of NaBr at 40 deg C.

To retard all fog, try using Tetra Aza Indene, sold by the Photographers Formulary either as powder or pre-prepared solution.

PE

hrst
11-02-2009, 06:04 PM
Oh, the fog was (at least mostly) safelight fog! It seems that erythrosine gives quite good sensitization even to yellow wavelengths.

Our orangish-red LED safelight won't fog any multicontrast enlarging paper at all, but 1 minute from 15 cm distance gives almost dmax on our emulsion -- that corresponds to about one hour at 100 cm in black room. We used the same safelight in the first, non-erythrosine emulsion.

We used the safelight all the time. Now we know what to do: go towards longer wavelengths (625 nm), reduce safelight level as much as possible and use it only when necessary.

It's very reassuring to note that the wash is probably not the main culprit, or a culprit at all, and that the spectral sensitization really worked quite well.

dwross
11-02-2009, 07:51 PM
Congratulations on the great detective work and your ever-improving emulsions! It's a lot of fun to hear about the progress of your work. Thanks for sharing.
d

filmfabrik
11-09-2009, 09:47 AM
hrst,

i am fascinated of your results, too - thank you very much for sharing them!
You said, that you would like to try some extracted chlorophyll as red sensitizer - (how) did it work?

best regards,

Peter

hrst
11-09-2009, 10:25 PM
filmfabrik,

We have not tried chlorophyll yet. I have it extracted but we'll first try to make a proper ortochromatic emulsion with little fog and more speed. Then it's time to try chlorophyll...

Currently we are working to make electron bombardment machinery to "sub" PET. I just made a working high voltage source using flyback transformer but I got barely 5 kV, it's not probably enough. Voltages to 20 kV should be easily possible so I have to redesign it a little. But, this is not so complicated (nor dangerous) as it may sound.

PE, do you happen to have some specific information about acceleration voltages needed for PET electron bombardment :D?