Emulsion seems to react with nitrile gloves.

Discussion in 'Silver Gelatin Based Emulsion Making & Coating' started by Nodda Duma, Jan 22, 2018.

  1. Nodda Duma

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    As I work to speed up my plate-making process, I tried modifying the way I coat the plates. Rather than pour and tilt the plate around to spread the emulsion, I lay the plates down on a flat surface and spread the emulsion with my gloved finger. This worked well at first, but then I ran out of gloves and bought different ones (nitrile gloves, which I would wash in soap and water after putting them on). When that batch went out, I got questions about "swirly" artifacts in the emulsion which unfortunately show up in the image after development. After some investigation, I determined that the swirlies resulted from some interaction between the nitrile gloves and the emulsion. Spreading the emulsion with a glass rod, acrylic puddle pusher, or the stainless steel tip of my syringe made a nice coating without swirlies (so I'm doing that going forward).

    That was kind of surprising, and frustrating as well since they went out to other folks before I caught it. The "swirl" is darker in the developed image, so I'm guessing the nitrile rubber somehow reacts to increase the sensitivity (or fogs) the emulsion?

    Not sure if the same thing happens with Latex gloves.

    -Jason
     
    Last edited: Jan 22, 2018
  2. Photo Engineer

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    Never saw this or heard of this. I have no idea what is going on, but perhaps a surface effect.

    PE
     
  3. OP
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    Nodda Duma

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    Yeah it was a new one on me. The surface effect is plausible. I was also thinking maybe some contaminant on the gloves if it weren't the nitrile itself (sort of a cop-out argument.. I can't verify it but I can mitigate it). I'll try to get some pictures. Otherwise the plates are coming out awesome.

    The stinker is that it doesn't show up until *after* the emulsion has fully dried. That is, it looks perfectly fine when wet, looks great when the gelatin sets, and then BAM a swirlie when I check the dried plates the following morning. I can claim it's a "feature of the hand-crafted nature of the artisan plate-making process", but I'd be wading through it pretty deep. I'd rather the artifact be gone. :smile: My lesson learned is not to touch the wet emulsion with my finger, glove or no! So I machined an acrylic puddle pusher for larger plates. For the smaller plates I ordered the type of glass angled rod that medical folks use to spread bacteria culture around in a petri dish. The gelatin thickness is controlled by the amount I lay down with a syringe.
     
    Last edited: Jan 22, 2018
  4. Photo Engineer

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    It could be the mold release agent still clinging to the gloves. IDK, but good luck.
     
  5. MattKing

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    Could it be the soap you used to wash the gloves before using them?
     
  6. AgX

    AgX Member

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    There is no release agent used at all.


    Instead a coagulant is used:
    Calcium Carbonate, Calcium Nitrate, Acetic Acid or Hexacycloamineacetate. All of these I consider above suspicion.

    I rather think of the sulfur compound used in the rubber compound.
     
  7. chrisaisenbrey

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  8. OP
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    Nodda Duma

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    I coated a bunch of plates last night - whole plate, quarter plate, and 12"x20" plate, and spread the emulsion around usising the acrylic spreading rod that I made and avoided touching with my gloves. I saw no "swirlies".

    MattKing: I thought dish soap the other night, but it's the same dish soap I use to clean and prep the plates as well as wash all my equipment (just common stuff..Ajax I think). I was much more thorough in rinsing my gloves than the plates, so I'm probably safe inferring that the issue is not the dish soap.

    For now at least I know how to prevent them from occurring, which is a good thing.

    -Jason
     
  9. OP
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    Nodda Duma

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    I'm about out of emulsion again, so I'll be making more. That made me curious enough to estimate I've coated the equivalent of about 1000 4"x5" plates in the past month.
     
  10. Photo Engineer

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    Those chemicals Agx mentions and the sulfonate you mention are surfactants / release agents.

    PE
     
  11. AgX

    AgX Member

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    The chemicals I mentioned are used to start a coagulating/setting reaction of the latex pulp and are most importing in forming a rubber layer on the mold. They are not used as release agents in the common sense, as in common molding.
     
  12. pentaxuser

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    I feel sure there is somebody in the U.S. who is an expert with such claims and I cannot but help feel that I have seen/heard examples but I am not sure if he is a member here :D

    On a slightly more serious note and simply to expand my knowledge can I take it that even depth of emulsion is unimportant?. Using a finger to spread emulsion anything like evenly must be a nightmare with a finger, surely?

    Thanks

    pentaxuser
     
  13. OP
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    Nodda Duma

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    No, it comes out very even or I wouldn't have tried (even verified with measurements of the emulsion depth and not just by eye). This is done while the emulsion has not yet set up. As I mentioned, I absolutely could not tell which plates would have the artifact and which do not until the emulsion dries fully. The bad plates come out perfect, with smooth finish, except the swirl mark has a different shade.
     
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  15. Photo Engineer

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    Hexacycloamineacetate (sic) is probably a surfactant here.

    PE
     
  16. OP
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    Nodda Duma

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    I dug through and found a plate with the artifact.

    IMG_1525.JPG

    You can only see it in reflection from the light.

    Head-on you cannot see it.

    IMG_1529.JPG

    As you can see, otherwise the plate looks really good. When I stopped using my gloved finger to spread the emulsion around, the artifact went away.
     
    Last edited: Jan 23, 2018
  17. OP
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    Nodda Duma

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    I've now seen swirlies when using a glass rod to spread the emulsion, so I can't claim correlation with the nitrile gloves.

    I sketched up a fault tree analysis to look at all aspects of the whole process. After eliminating the obvious non-causes, basically the fault tree was telling me that the source is either a contaminant (containers, coating equipment) or an issue with the process (glass prep, coating, cooling). That analytical conclusion even makes sense. I've also had coating runs without swirlies, so reviewing my notes helped me eliminate some other sources (like the kids) and reduce the failure mode testing to a few variables. So I did tthat yesterday (some things I kind of knew the answer, but wanted to explore coating process variables anyways). Here is a summary of the testing. In all cases ambient temperature controlled to 70F (and plates are also at that temp when they are coated ... that hasn't changed since I started coating glass two years ago, which was a potential cause I was able to check off without having to test).

    Temperature: Control group emulsion applied at 101F. Variable group coated at emulsion temperatures ranging from 100F down to 79F. Quality of coating got worse below ~90F, degrading significantly with lower temperature, but no real "swirly" correlation. (saw swirlies and good coatings in both groups).
    Coating technique: Hand, glass rod, tilting of plate, glass rod not scraping substrate. No correlation (saw swirlies and good coatings in both groups)
    Subbing layer: With and without subbing layer. No correlation (saw swirlies and good coatings in both groups)

    Pulled out a new syringe, looked at the plunger and noticed a viscous liquid apparent on the unused plunger. What! My guess is a silicon lubricant, which explains why the plunger was so easy to operate. So that leads into contaminant testing.

    I washed the components of that syringe in dish soap and warm water as best I could and marked it so that I could coat plates with the cleaned syringe and with a newly opened, untreated syringe. A correlation! And a moderate-to-strong one at that. Swirlies were much less apparent with the cleaned plunger, but still not completely gone from test plates. It could be that I didn't entirely clean the silicon off. After the correlation testing, I coated a couple dozen additional plates for my own use, and used the cleaned syringe to do so. This morning I noticed that those plates look very good, so as the evening (early morning actually) went on, the plates got better possibly because the rest of the silicon cleared out from use. I need to switch brands of syringes to follow up.

    Emulsion from different storage jars: I divide batches up into smaller ceramic jars for storage until I need them. In this way I don't continuously reheat all the emulsion in the batch. There's a potentially mild correlation. I switched to using just the clean syringe about the same time I broke out a new jar of emulsion, but unfortunately my notes aren't as clear as to exactly when two events happened. So I need to follow-up on this one.

    Air circulation during emulsion drying. Mild correlation with plates closer to the fan vs. farther from the fan vs. plates with no circulation. Could be tied as well to switching to using the cleaned syringe, as plates from earlier in the testing were placed nearer the fan in my drying setup. Additionally, I've always used a fan blowing on the plates to help speed up the drying process so that hasn't really changed from the past few years. I will follow up on this as well.

    The evidence strongly indicates contamination in the brand of syringes I recently started using could be the culprit. I had just bought new packs of syringes about the same time as the swirlies started showing up, and they are different than the brand I've used before. I might have been misled in earlier testing as the syringe would clean out from use, and then the swirlies could have come back when I switched to a new syringe. Plates coated solely with the "good" syringe were significantly better looking, and in fact most of them (the later ones as explained above) were entirely clear of swirlies. However, there are a couple of additional variables I need to follow up on, and the plates with no circulation still need to be examined once they are done drying. I'm also going to break open a new syringe and intentionally contaminate a plate with the lubricant I find on it.

    I guess my question would be if there's potential for interaction between the emulsion and silicon lubricant? I'll find out when I do follow-up testing.

    So bottom line is to never assume that what should be clean and contaminant-free actually is!

    Some of the results were good news hidden in the bad "swirly" results .. the lack of correlation to actual coating technique (smearing with fingers, spreading rod, or tilting the plate around) was the big one, because it clears the path to adopting faster production techniques.
     
    Last edited: Jan 31, 2018
  18. Jens Hallfeldt

    Jens Hallfeldt Member

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    Dear Nodda Duma,

    many thanks for the detailed and interesting post.
    One question: What coating technique gives you the most even emulsion thickness?

    Best
    Jens
     
  19. OP
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    Nodda Duma

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    Hi Jens,

    They all do, honestly. I've found that working quickly and efficiently is more important than the actual technique you choose, in that the key is giving the emulsion enough time to finish evenly distributing itself on the surface of the plate before setting.
     
  20. Jens Hallfeldt

    Jens Hallfeldt Member

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    Hi,

    I see. Thank You.
    BTW good that your plates have nodges like sheet film, something I was missing on the vintage plates I've used...

    Best
    Jens
     
  21. Photo Engineer

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    Veterinary syringes are not lubricated. They are sold by most vets at a huge markup, and at a more reasonable price from the Photographer's Formulary. Also, for coating, I use Monoject syringes. In bulk they are quite reasonable in price.

    PE
     
  22. OP
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    Nodda Duma

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    That was the name I couldn't remember. Now that I've looked, Kendall Monoject was the brand I started with, and they worked great. I got them because Kendall is my sister-in-law's name. Total coincidence. Unfortunately, when I ran out I couldn't recall the brand. So I ordered this BStean brand (great for glue and oil dispensing applications).

    You can get the Monojects off amazon as well for incredibly cheap.

    I think the key is probably to order syringes for oral or medical applications.
     
    Last edited: Jan 31, 2018
  23. OP
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    Nodda Duma

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    The box of Kendall Monoject syringes arrived today. Upon inspection, they also show evidence of some kind of lubricant on the plunger. Not as much as the brand that caused problems, but nevertheless the lubricant is evident. I'll be returning them.

    I bought another brand used for giving measured amounts of oral medication to kids. Those also had lubricant on the plunger. Think on that for a moment.

    Finally, as a backup plan, I ordered a glass syringe, 10ml, with what's called a Luer-Lock tip for which I also ordered 1" stainless steel dispensing needles (blunt tip). Glass syringes are *all* glass, the plunger being tightly toleranced so that surface tension of the fluid is sufficient to keep it from leaking past the plunger. It arrived yesterday. I used this glass syringe to coat plates last night, spreading the emulsion with my glass rod spreader. The plates came out flawless.

    So if you are to use a syringe to dispense emulsion onto the plates, I can only recommend obtaining a glass syringe. They are about $35 shipped on amazon.

    Of course, pouring the emulsion as commonly described will avoid this source of contaminant as well.

    -Jason

    P.S. The glass syringe is a very refined-looking piece of equipment. Almost a work of art.

    IMG_1554.JPG
     
    Last edited: Feb 3, 2018
  24. Photo Engineer

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    Jason, the Monoject syringes I have are problem free and I have used them for over 10 years on all aspects of making and coating. The SS versions as shown tend to corrode easily so check them out. The SS is generally low quality.

    PE
     
  25. OP
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    Nodda Duma

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    I used the Monoject syringes for years as well, with no apparent issues. Admittedly I never looked for this specific problem and in fact it is difficult to see the artifact itself unless you hold it just right in the reflected light. Perhaps it was there all along but not in sufficient quantity to manifest in the developed plate? I'll take a look at older plates I still have.

    Otherwise, I can only report what I observed of the Monojects I just received. The potential for contamination definitely exists. I'll let others draw their own conclusions regarding the use of Monojects. To summarize, actual use indicates no apparent problems. Inspection indicates the potential exists for problems.

    The takeaway is to pay attention to all of the equipment that comes in contact with emulsion! :smile:

    The syringe I acquired was made in Germany by Fortuna, and as a medical device must meet certain manufacturing requirements. So they should be able answer if I enquire about the type of stainless steel used. I'll report what I find. There are slip-fitting versions of the glass syringe available as well, if the stainless steel is a concern. I've been cleaning mine after use along with the other equipment.

    Here is a link to a lower cost source of the glass syringes. Both Luer Lock and Luer Slip tips are available for $10 ea. Wish I had found that earlier.

    https://www.air-tite-shop.com/c-13-glass-syringes.aspx
     
    Last edited: Feb 4, 2018
  26. OP
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    Nodda Duma

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    I heard back from the manufacturer. The metal is actually Nickel-plated brass, which I'm happy with from my former Navy perspective of designing for corrosion prevention... but I'd love to hear your take, Ron
     
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