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  1. #1
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    Making a modern emulsion

    For the last several months I have been working on the calculations and preparation for making a new, high speed emulsion.

    Basically, it is a high iodide, coarse grained emulsion that uses vAg control or detecting to get to the "right place".

    It required about 2 hours prep, and about 3 hours run time, but this did not include the months of calculations and attempts to buy tubing and set up the vAg control. There are several posts on both of these here on APUG.

    In any event, I finally go the #13 tubing that allowed me to make a 1 Liter run which used nearly 1/2 pound of silver or about 250 grams. Wow! Anyhow, over the 3 hour run, I was off by 1' 30" which is not bad. It took me that extra time to get to the vAg calculated so I felt pretty good. One liter is the minimum that can be made with all peristaltic pumps that I have found on the market. Changing flow rate will not give the right results.

    Now for the problems.

    1. It was very foggy due to the high speed and probably small light leaks over the 3 hours. (or me )

    2. There was a lot of aggregate formed, probably due to poor mixing and the very low pump rates needed for such a small batch. This is inevitable. I will need to achieve probably 4000 RPM with a strong mixer as I could only get to 700 RPM with a magnetic mixer. In addition, I may need baffles in the beaker to break up the eddy currents and etc. to allow better mixing.

    This is beginning to convince me that making modern emulsions is going to price itself out of the range of most makers due to the requirements.

    I have also found that the automated equipment that might be desirable is quite pricey as is the very simple tubing and the tubing is very hard to get.

    So, I have what may turn out to be an ISO 400 emulsion but may take me weeks to get there requiring calculations to figure out the sensitization needed for this emulsion and the amount of antifoggant to prevent total fog formation.

    I will try to update this as I can. This will probably be in "the book" which is in version #5 and the changes have all come from suggestions after reads by associates and friends.

    My thanks to them.

    I would like to add my thanks to my wife for her patience with me. She broke her leg last year and spent a year recovering with 6 months in a wheel chair. This kinda slowed me down. This is my first public comment on this, and I mention it to help explain some of the delays. Sometimes, the best laid plans .... etc. Anyhow, my apologies for being so tardy.

    PE

  2. #2
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    I'm very impressed at the fact that you are really only 1min30sec off from the calculated 3 hours. It sounds quite incredible (at least to an amateur like me) and kind of proves your theory. So, congratulations! Thanks for sharing this experience, and we'll be waiting for any progress in this field.

    Can you elaborate a bit why wouldn't smaller runs work? Is it just a problem with equipment (peristaltic pumps that need certain minimum volume), or is there some more fundamental reason in the precipitation/ripening of silver halides in the emulsion itself? I still believe that stepper-motor controlled syringes could be used to feed exact and small volumes of liquids instead of peristaltic pumps, but that would need quite a bit of engineering.

    How foggy is it, can you get a picture at all?
    Last edited by hrst; 05-23-2010 at 01:08 PM. Click to view previous post history.

  3. #3
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    At 1 Liter make size, the starting flow rate is near the lower limit of the pumps range, even with the very fine tubing I used. And, the chemistry was coming out in tiny drops rather than a steady flow. I cannot go any slower and backpressure in the tube did not seem to give any significant help.

    At a "normal" size such as 10 L, the flow rate would be in the middle of the pump range even with larger tubing, and I could help with backpressure to give a steady stream. Of course that would use about 2500 g of AgNO3.

    I have one wedge spectrogram. Being unsensitized, it is very low contrast.

    PE

  4. #4
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    Maybe a 5 ml syringe with a 0.5mm or 0.6mm needle could be used in the beginning to give a very slow but steady flow. The tip of the needle would be in the emulsion kettle. After the first 5ml you could automatically move to bigger syringes and needles that give bigger flow rate with less accuracy. So you would divide the solution into several syringes, controlled by motors by computer. This would need quite a bit automation, though.

  5. #5
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    I cannot buy syringes with needles in the USA without a prescription from a Doctor. Besides, using the hand held syringe makes it difficult to accurately ramp up the flow rate. And, this must be done with 2 solutions, Silver and Salt. I did try a syringe with a plastic "needle" for backpressure, but I could not get the flow rate down low enough, nor hold it constant enough, nor ramp it well enough.

    Believe me, using a syringe of some sort was one route I explored, along with several dummy water rehearsals to fine tune my technique using several methods.

    PE

  6. #6

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    There's quite a bit of options available for peristaltic pumps with low flows. And small tubing is available from companies like Irama Corp - see this page for a list of small ID tubes that are designed for lab grade pumps. http://www.iramacorp.com/pump.tubes.htm

    The smallest one, labelled "orange/black" can pump at 0.006 ml/min with a pump running at 0.5 rpm. That's pretty slow to me! Purple/White will get you up to 22 ml/min at 90 rpm - so there's a huge range of flow options available out there.

    You're certainly right that there are issues with low backpressure and flow variability when using such small flow rates. But you can also get some pretty fine tubing for dispensing the liquid - much finer than regular syringe needles. My understanding is that 21 gauge is a commons size for drawing blood, and 30 gauge for insulin needles.

    www.smallparts.com sells teflon (PTFE) tubing down to 44 ga. That's 0.002 inch diameter. I've got some from them that's 32 gauge. Even at small flow rates, that diamter will help smootly dispense the liquid being pumped.
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  7. #7
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    Yes, you are correct Kirk, but not all tubing works with a peristaltic pump. I got several types of fine tubing that just refused to move fluids at all using a peristaltic pump. This helped run up the cost to me, getting tubing.

    You see, OD is critical to achieve proper "contact" with the pump rollers, and ID is critical for flow rate. Flexibility is also critical to allow the rollers to compress the tubing. So, I have piles of tubing but only one type that works.

    Here are the specs on the one that works: http://www.coleparmer.com/catalog/pr...sp?sku=0642913

    I have 3 rolls each of #13 and #16 which fit my flow ranges. I have 2 universal pump heads that will take sizes from #13 up and one that will take #16 only. And, BTW, the type of tubing that works will not work with any sort of pressure at all except mild backpressure. It will also not tolerate much over room temperature.

    PE

  8. #8

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    I cannot buy syringes with needles in the USA without a prescription from a Doctor. Besides, using the hand held syringe makes it difficult to accurately ramp up the flow rate. And, this must be done with 2 solutions, Silver and Salt. I did try a syringe with a plastic "needle" for backpressure, but I could not get the flow rate down low enough, nor hold it constant enough, nor ramp it well enough.

    Believe me, using a syringe of some sort was one route I explored, along with several dummy water rehearsals to fine tune my technique using several methods.

    PE
    Thats a bummer about the syringes. I never thought about them being illegal. In NH you only need to be 18 or 21 to buy them at rite aid. Pack of 20 was like 10$ or so. There was only one rite aid in the city I was at that sold them. It's amazing what you learn at art school

    Alex
    p.s. To the best of my knowledge, the main use for the needles were tattoos.

  9. #9
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    Alex;

    You can buy a syringe here with an open end, but you cannot get the fine needle or anything that is related to it here in NYS. Too much regulation.

    As for pumps and tubing, I have been round and round about this. One company got me tubing and swore it would work. Then they tested it with a 5 or 7 channel peristaltic pump and found the tubing would not work, so they reordered for me. This has been a real problem.

    PE

  10. #10

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    No syringes with needles here in Oregon, as far as I know. Too much heroin use in the past for that.

    PE - you are certainly right about different pumps have to be matched with different tube diameters, thickness, and flexability. The tubes I listed to are used in a large number of analytical lab pumps and are often found used for sale.

    I think it shows that one pump may not be able to fill every emulsion makers needs, depending on the flow rate needed.
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

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