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  1. #1
    hrst's Avatar
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    Making my first emulsion now.

    Hello,

    Today we started making an emulsion for a first time. It's now standing in room temperature over this night, and tomorrow we'll proceed to noodle wash. If you don't mind, I'll post our process here just to make sure it's okay and maybe get some tips .

    First, I started by making silver nitrate. Silver should have been pure and nitric acid was 60% laboratory quality. I evaporated all the nitric acid, added distilled water and evaporated it. Still, it wasn't 100% white but a very little gray and smelled a little (some residual nitric acid?). I hope it's okay...

    We followed the formula in PE's topic "A real formula", but made only 1/10 of it. We substituted 11,41 g of sodium bromide for 13,2 g of potassium bromide. We used food gelatin, not powder but "sheets". It doesn't say anything about additives but that it's made from pig skin.

    We heated silver nitrate solution (B) to about 45-50 C and added ammonia. First it got yellow, and then completely clear. It took maybe about 5-20 ml of ammonia for 50 ml of B. (Didn't measure though.) Oh yeah, looking good at this point!

    We heated A on hotplate magnetic stirrer to 45C and B to 45C in water bath.

    We started adding B to A, about 5 ml at a time, every minute. It took 12 minutes to do this. B wasn't in water bath any more so the temperature dropped. But the hotplate stirrer has a sensor so it keeps the emulsion at 45C all the time.

    After B was added, we kept emulsion at 45C for 30 minutes, keeping the stirrer going. Shut down the safelight for this time.

    Then we poured emulsion to five 35 mm film containers. We left three of them to room temperature, about 25C, and two of them in refrigerator at about 10C. It takes some time to cool down, because we put the film containers in a plastic processing tank (because it's lighttight).

    Tomorrow, we are going to add gelatin if necessary and noodelize some emulsion, wash (until wash water shows no crud when added some silver nitrate), and add gelatin. No sentisizers yet. Right?

    And then coat some overhead projection transparencies (not the laser-ones but the cheapest ones, they are perfectly smooth like film base, I think they are acetate). We made a simple coating blade with about 10mil gap.

    Now, is everything going well? At least it was very fun! Any tips & tricks for tomorrow?

    I poured some emulsion on OHP transparency and dried it with hairdryer, then exposed to light and developed in paper developer. It got black! So it basically seems to work. But it needed much light.

    I'll post results.

    I've extracted some chlorophyll from leafs using acetone, we are going to experiment if it could be used as red sentisizer. But there will be so much to do before that point... If we can even get a decent blue-sensitive emulsion first!

    PS. HUGE thanks to PE, your information about emulsion making here is priceless!! Thank you thank you thank you.

  2. #2
    Ian Grant's Avatar
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    The storage temperatures are important. Overnight at room temperature with no additives is a potential problem.

    Something that I've not seen mentioned at all on PUG is the importance of digestion/ripenening times & temperatures, these can make a very significant difference to the speed & contrast characteristics of an emulsion.

    Ian

  3. #3
    Photo Engineer's Avatar
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    Have fun.

    Make sure that the emulsion has set up to a gel before you noodle it, and use cold water. The whole process should be carried out at under 20 deg C, usually about 10 deg C. to keep the noodles from swelling too much. Wash free of ammonia odor and as much residual salt as possible and adjust the pH to about 6.0 with dilute sulfuric acid (3 - 30% max) if it is still basic. If it becomes too acid, below 6.0 then use 4% sodium hydroxide to bring it up to about 6.

    If you don't harden the coating, you will have to preharden with formalin solution or chrome alum solution.

    PE

  4. #4
    Photo Engineer's Avatar
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    Quote Originally Posted by Ian Grant View Post
    The storage temperatures are important. Overnight at room temperature with no additives is a potential problem.

    Something that I've not seen mentioned at all on PUG is the importance of digestion/ripenening times & temperatures, these can make a very significant difference to the speed & contrast characteristics of an emulsion.

    Ian
    Ian;

    This particular SRAD can use up to 1 week at 4 deg C for digestion and / or a digest of 1 hour at up to 50 deg C or a digest of 4 hours at RT. So, it is quite robust in this sense.

    The time and temperature will affect speed and contrast though.

    I would add that with food grade pig gelatin, I have no idea what they will actually get. This formula was designed for photo grade inactive bone (cow) gelatin.

    PE

  5. #5
    hrst's Avatar
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    Thanks for answers. Yes, I'm very interested about this gelatin, whether it will work or not -- of course it would be cool to be able to use basic, non-photographic ingredients that are easily available also in smaller countries. And I'm also interested about how much it has sulfur, so what ISO we will get without hypo. I will definitely post results in any case!

    Quote Originally Posted by Photo Engineer View Post
    If you don't harden the coating, you will have to preharden with formalin solution or chrome alum solution.
    I found from some post here that 0.125 g chrome alum would be about right for 160 ml of emulsion. But if I get formalin, how much should I use it, and how concentrated?

    If I coat medium format roll film, maybe I should add an overcoat also? Is it done after drying the first coating for, say, one day at RT? Is it just gelatin + formalin or chrome alum?

    Now, am I right that hypo (and possibly gold chloride) is added after noodle wash? Is it done before or after gelatin level fix?

    Thanks a lot for helping us out!

  6. #6
    Photo Engineer's Avatar
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    If you preharden in a bath before the developer do the following:

    10% Chrome alum OR a formalin bath as follows:

    Formalin 37% 10 ml
    Sodium Sulfate 50 g
    Sodium Carbonate 50 g
    Water to 1 L, pH 8 - 9 with NaOH or H2SO4 (4%)

    Treat coating for about 5 minutes in either of the above hardeners and then wash for 5 mins at 20 deg C, then go on with your normal process.

    Do the hypo + gold after the wash and gelatin addition. Pig gelatin will offset any figure I might give and so it will probably have to be done by trial and error. Sorry.

    I don't suggest that you coat roll film. Coat sheet film or plates.

    PE

  7. #7
    hrst's Avatar
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    Today we started where we left yesterday: first half, digested in room temp overnight; and second half, digested in refrigerator overnight.

    We melted the emulsion and proceeded to noodelization (nice word huh?? ). We found out that it required about 13 g / 100 ml of food gelatin to become proper gel for noodeling and the final level was about 15-16 g / 100 ml to coat properly. That's quite a lot, isn't it. We had to heat and cool down the emulsion many times before we found this gelatin level, so maybe there is too much digestion now. The second batch went better, though, as we knew this high gelatin level.

    Maybe this pig gelatin is needed in larger amounts. Maybe I should change the starting point also, eg. 30 g/l --> 60 g/l.

    We washed for about 40 minutes and, still, wash water sample showed some deposition with silver nitrate test solution. We decided to stop washing at this point. When melted again, it had a little ammonia smell, but not much. I think our noodles are too thick (about 5 mm) and thus wash slowly. Have to get better noodler. As we didn't have an access to a pH meter, we didn't do any adjustments now...

    We coated the first half that was in room temperature overnight. No sentization. After coating, chilled for a minute or two in refrigerator and put to room temp. Not quite uniform yet. But the third one started to look good! I think we'll learn it by doing .

    We also washed (but not coated yet) the second half that was in refrigerator overnight and divided it into three further batches: A) no sentization; B) 9 ml of 1 g/l hypo per 100 ml emulsion; and C) 25 ml of 1 g/l hypo per 100 ml emulsion. For every batch, we added the hypo solution and then stirred for 3-4 minutes. We put these in 5 C refrigerator and we will coat them on Monday. I hope it keeps until that.

    Emulsion splashes on the table were beautifully yellow and got very black quite quickly when we poured some developer on them!

    And, what's best, it was very fun again! If you don't mind, I'll continue posting to this thread about our experiences. Many thanks for tips and for bearing with us,

    Antti Alhonen & Matti Hautala
    Finland.

  8. #8
    Photo Engineer's Avatar
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    Well, firstoff, gelatin comes in grades indicated by Bloom Index. There is a rough correlation between BI and viscosity. Food gelatin is low in BI in most cases, around 75, while Photograde is around 250. This means that Photograde would be more "chewey" if you ate it.

    So, you may need more gelatin to get to the best coating point.

    Next, you cannot test for halide presence or salt presence when the emulsion is still alkaline. You will get Silver Hydroxide and also other Ammonia complexes of Silver, so you either have to make it acidic with H2SO4 first or wait until the ammonia odor is gone. Otherwise, the test will fail.

    Lastly, I cannot help you with the hypo level at all, but what you gave sounds high to me, but then you are not heat treating the emulsion so IDK what will happen.

    Best wishes.

    PE

  9. #9
    hrst's Avatar
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    Hardening

    This hardening thing still seems like a mystery to me... I've read dozens of threads here in APUG during last weeks but everything is mixed up in my head and it's difficult to find the information again.

    So, let me rephrase: there are at least three different things:

    1) A subbing layer, that may be needed for adhesion of emulsion. Includes chrome alum or formalin?
    2) Hardening of the emulsion itself. If made with formalin, takes some time to harden and can fog if kept for too long. Formalin was used in films decades ago?
    3) Overcoat that protects emulsion. Needed if film is wound up on a roll. This also includes chrome alum or formalin?

    Hardening of emulsion is compulsory, sub and overcoat only if needed. And, hardening can be omitted if emulsion is hardened after exposure, before processing, and that is called prehardening. Am I right at all ?

    Can I add that formalin hardener to the emulsion just before coating? How much I should add it? I have understood that it may fog the emulsion if not coated right away. How about coated film if not exposed right away, how quickly it will fog? One day? One week? One month? One year?

    Thanks,

    A.A.

  10. #10
    Photo Engineer's Avatar
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    You havae things essentially correct, but.........................!!!

    I use glyoxal as it is less toxic.

    You add the hardener just before coating. You must begin coating then. It will harden if not coated right away. After coating, fogging is slower but depends on the emulsion.

    You may leave out hardener and then use a prehardening solution (given in my post above) just before the developer as follows:

    Preharden
    Wash
    Develop
    Stop or rinse
    Fix - hardening fix suggested
    Wash
    Photo Flo if film or glass
    Dry

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