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holmburgers
01-26-2013, 04:59 PM
Howdy all,

One of the perks of being at GEH is the conservation lab. Not only do they have a bunch of awesome microscopes, but they have people that know how to use them!

Mark Osterman brought in a couple of old Polaroid precipitation nozzles (needles for introducing silver-halide into the emulsion pot) and I wondered how big the openings were. I asked Ralph Wiegandt (http://www.loc.gov/preservation/outreach/tops/wiegandt_ravines/index.html) if he could measure them somehow and he showed me how to do it on the microscope. These are at 50x.

There are 3 images; two metal nozzles that were originally used by Polaroid and a glass nozzle, hand pulled by Mark that we use in the emulsion lab here at GEH. The metal ones measure 0.6mm and 1.2mm; the glass one is also (miraculously) 0.6mm.

In hypodermic needle gauges, this translates to 16g and 21g.

To me, this brings up an interesting quandary. The same quantity of silver-solution can be introduced into the gel/halide "pot" in a set amount of time, yet the nozzles can be bigger or smaller. The effect being, to increase the pressure at which solution enters the pot.

On one hand you can have an incredibly fine stream of high pressure going through a very small nozzle, and on the other hand you can imagine a large nozzle that just "drips" out.

So how important is the nozzle size and the pressure?, or is rate of addition the more important factor??

dwross
01-26-2013, 06:34 PM
Hi Chris,

Nice to see you again. Good to see you're having so much fun at GEH!

re: "So how important is the nozzle size and the pressure?, or is rate of addition the more important factor??"

It's hard to imagine all the alchemy and uber engineering that was engaged in to make Polaroid products, but this film, http://thelightfarm.com/cgi-bin/showvideo.py, starting at 7:56 minutes gives an idea of how important extreme precision was to Kodak, not all that long ago. (Spoiler alert: NOT :))

d

AgX
01-27-2013, 02:35 AM
A "jet" compared to a "drop" delivering both the same flux (volume per time) would have a larger surface.

holmburgers
01-27-2013, 12:48 PM
Haha, wow Denise, you're not kidding. There's no way they were really making film like that by that point... right?? ;) I didn't quite realize what all went into getting that film translated; what a great service you guys did in doing so!

A "jet" would also reach further into the solution and produce much more turbulence on its journey. I posed this question to Ron and he said that a high pressure jet will remain "cohesive" (I believe this is the word he used...?) longer and thus delay the reaction slightly. But on the other hand there is more surface area, and you'd have to think that the turbulence that it encounters would also aid in quick mixing.

Who knows though; it's all arm-chair emulsion making at this point. It'd be nice to make the same emulsion with a "drip" and a "jet", with the same total rate of addition, and compare the two.

Hexavalent
01-27-2013, 12:53 PM
I use 24 gauge needles, directed as closely as possible to the stirrer. So far, I've never had any "crunchies" or pepper grain, except when I once used a larger bore needle. 24 ga. and finer does require quite a bit of pressure for quick delivery!

holmburgers
01-27-2013, 01:09 PM
Very interesting Ian; that's quite a fine nozzle indeed. How large of a bore are you referring to when you mention the crunchies??

You bring up a good point about delivery; a high pressure nozzle would make a long addition easier and more consistent, compared to low pressure where the accuracy of delivery is all controlled by your muscles. With high pressure you kinda just 'give it hell' and it ejects as fast as it can. We've been using Mark O's bulb thingy which works on that principle; you squeeze it 100% and the rate is more or less controlled by the constant pressure you've created in the system.

And then there's this (http://www.syringepump.com/NE-300.php) option (warning: eye candy)...

Hexavalent
01-27-2013, 01:41 PM
Chris, the larger bore item was one of those hardware store syringe thingy designed for glue, probably 1mm. It was very tricky to achieve a steady delivery. Basically useless.

kb3lms
01-27-2013, 05:41 PM
I 've made myself a hand crank syringe pump and use 18 gauge needles and nylon (I think) tubing. The tubing came from empty hair spray bottles. It's not really not that hard to control delivery rate. Below is a picture.

https://www.dropbox.com/s/5pk29gtcjxuy5fp/IMGP3608.jpg

The tubing arrangement is likely to change a little because the clothespin tends to move around on the side of the pot and the tubes don't really point were I want them to. Also, been thinking about changing to a smaller sized needle.

I think the part about the cohesiveness Ron mentioned to you is that the high pressured streams push away the other liquids and allow the salt and silver reactants to combine at a more closely controlled ratio. So, the crystals are nucleated within the stream and then carried away into the rest of the emulsion. You want to have the reactants introduced sub-surface.

Orioes
01-27-2013, 08:55 PM
Hi Chris,

Nice to see you again. Good to see you're having so much fun at GEH!

re: "So how important is the nozzle size and the pressure?, or is rate of addition the more important factor??"

It's hard to imagine all the alchemy and uber engineering that was engaged in to make Polaroid products, but this film, http://thelightfarm.com/cgi-bin/showvideo.py, starting at 7:56 minutes gives an idea of how important extreme precision was to Kodak, not all that long ago. (Spoiler alert: NOT :))

d
Wow, you know I knew mass production of film was a major industrial undertaking and it was in its time the largest consumer of silver but that never really hit home till I saw the office building sized film base machine or the guy shoveling in silver ingots by the gross. Very cool movie.

holmburgers
01-27-2013, 11:37 PM
I see what you mean Ian; it does seem like one would need a little back pressure to get a steady delivery.

Jason, wow, that's great! Just this week the idea of syringe pumps hit me, but it's great to know that others have already been thinking about this stuff.

I've been mulling over a design in my head... imagine that the syringe (or pump) is seated on the counter, next to the kettle, with a length of plastic tubing leading to a hypodermic needle which is held in position over the pot by a lab stand. The stand could clamp a cork, through which you push the needle.

Regarding an 18-gauge needle; this is the size that seemed like a good fit to me, but I haven't used it in practice. I'd be very curious to know why you might be looking for something smaller; was it not ideal?

I was able to find some 18g needles in 4" length, which seems like a good length to work with. (here (http://www.shopmedvet.com/product/stainless-steel-hypodermic-needle-dz-18g-x-4inch/jorgensen-products-syringes-and-needles))

kb3lms
01-28-2013, 02:32 PM
Chris,

Good find on the needles on MedVet. I have bought plenty of syringes from them but never looked for needles, although I have only purchased the non-sharp type dispensing tips to date. And, I really don't want sharps laying around.

As for your idea of needles through a cork, you could do that. As you can see, mine works by attaching the needles to the syringe and the tubing leads to the kettle with the needles acting as an adapter for the tubing . The tubes are held to the kettle with a clothespin. The syringe pump sits on a stand (aka brick) next to the water bath (aka temperature controlled crock pot). So, in a sense, my pump is not really injecting with much pressure at all.

What you want to happen is that the liquid is injected subsurface and that you get all of the chemical out of the syringe and the line since AgNO3 is not cheap. If you are trying double jet, you want the reactants injected next to each other and I have seen some diagrams that even show an outer shield around the tubes or needles to allow the reactants to mix in a sheltered area.

Another thing I have found is that AgNO3 is building up in the stainless needle on the silver side. Actually it almost looks like metallic silver. I don't know if this is a conditioning effect or I should clean it out.

Mine is set up for double-jet, obviously, but I may "step back" to SRADs for a bit. DJ emulsions have shown to be kind of touchy in terms of finishing. I am guessing that in being more monodisperse, when things go wrong in terms of fog, it goes bad very fast, where a polydisperse emulsion gives a little more room for error. That's why I haven't mentioned anything about making DJ emulsions - I haven't made a good one yet without a lot of fog, although they do work. And no, so far, they aren't higher speed but they have been somewhat higher contrast.

I am thinking about a smaller than 18 gauge needle and tubing in order to get a higher pressure jet but I don't think it will make a night and day difference to the results. Maybe your design idea is what I am really looking for. But, how do you attach the tubing to the needle?

-- Jason

AgX
01-28-2013, 02:49 PM
I have bought plenty of syringes from them but never looked for needles, although I have only purchased the non-sharp type dispensing tips to date. And, I really don't want sharps laying around.

Sharp needle tips can be grinded flat. Best done with a micro-drill and a cutting disk.

JOSarff
01-28-2013, 03:41 PM
Chris,

Another thing I have found is that AgNO3 is building up in the stainless needle on the silver side. Actually it almost looks like metallic silver. I don't know if this is a conditioning effect or I should clean it out.

I am thinking about a smaller than 18 gauge needle and tubing in order to get a higher pressure jet but I don't think it will make a night and day difference to the results. Maybe your design idea is what I am really looking for. But, how do you attach the tubing to the needle?

-- Jason

Jason:

I think it's just Silver plating onto the stainless steel of the needle. If the Silver deposit in the needle is reducing the flow then I would suggest soaking the needle in a silver solvent such as Sodium or Ammonium Thiosulfate (Fixer).

There are adapters made that are female luer-lok to tubing and tubing to male luer-lok. The male luer-lok connection is where you attach the needle and place in the kettle. These may be available from the Vet supply Co. Chris mentioned earlier or eBay..

All the best,

Joe

dwross
01-28-2013, 04:11 PM
Silver plating is always a nuisance to keep in mind. Happens with glass stopcock burets, too. It's important to keep things rinsed out. I assume the reason to go with such elaborate tools as hypodermic needles is the hope that they will give you extreme precision (??). It sounds more like a set-up for spurious precision. I know that sounds like a harsh buzz-kill, but if there's even a little bit of gunk in a hypodermic, the changes in rate of delivery and the turbulence will seriously throw off your results. K.I.S.S.

Hexavalent
01-28-2013, 04:26 PM
Gunk in the hypodermic? I wouldn't use a needle twice for any purpose :)

Photo Engineer
01-28-2013, 04:31 PM
The mixing rate of a solution being added is dependent on flow rate, mixer speed, point of entry and solution concentration among a few of the variables.

A very concentrated solution can maintain its integrity for quite some time unless the stream is broken up by the mixer and even baffles which introduce turbulence to assist in breaking up bands or "tubes" of added solution. Imagine squeezing a tube of toothpaste into water. If you do it in a continuous stream you get a "tube" of paste in water. If you do it "somehow" in chunks, you get "drops" of toothpaste. It is the job of the designer to break up these pieces of whatever nature, in such a way as to achieve a good mix.

Now, our problem with Silver Nitrate is not as bad as using toothpaste but the analogy exists and if you add concentrated AgNO3 solution to water, you can actually see the "tubes" or "drops" and they vary with concentration, rate of addition and diameter or size of drop or tube.

You can experiment with this, as I did, with concentrated table salt or the like, with dye in it, added to plain water at varying rates, with different mixing and etc. This will "teach" you the optimum for any condition.

I get turkey basters at Home Depot, and I get large size (80 ml) from the Formulary. All of the tips have Luer connectors and I can exchange tips.

Expect some corrosion with cheap stainless. I try to stay with non-magnetic, non-plated parts, but this is not always possible. So, when things corrode I replace them. Oh, and standard tubing goes over a Luer male connector on a syringe and can be cut to any length and clipped in any position. I have shown pictures of that here on APUG.

PE

holmburgers
01-29-2013, 10:04 AM
Yes Jason, I'm amazed you are already going after double run emulsions; I figure there's enough to keep me occupied with SR and SRADs for a long time.. :) If you had a labstand and clamp like this (http://www.omni-inc.com/stand-assembly-for-tissue-master-homogenizer-p-43.html) (please don't spend this much money though...), you could easily hold a cork and mount the needle in that.

Unfortunately those MedVet needles are sharp; I thought they were blunt for some reason. It seems that grinding them down shouldn't be a nuisance.

The silver plating shouldn't be a problem, as Joe said, and as long as you flush your hypodermic needles with hot water after use and allow to dry, I can't foresee any "gunk" being a problem. The only thing that's going through it is silver-nitrate & water. I doubt that hypo will get rid of it since it's metallic silver though, which has effectively "printed out".

I honestly can't think of a more simple solution than hypodermic needles with standardized sizes. It's not about uber-precision per se, but about having a specific orifice that gives you the right "ejection" qualities; powerful stream, good back pressure, accurate placement in kettle. They're cheap and I also think that if you have the right s.s. needle, you should be able to reuse it as long as you want... but IDK.

Ron, with a simple magnetic-stirrer, would you ideally want the stream of AgNO3 to go right into the most turbulent zone, near the stirrer?

kb3lms
01-29-2013, 12:04 PM
Yes Jason, I'm amazed you are already going after double run emulsions

Yep, that's me. I had to try it. When I sit here at work waiting for the code to build or one of those "endless" meetings, well, you kind of zone out sometimes and ...


I figure there's enough to keep me occupied with SR and SRADs for a long time..

Yeah, don't be in a hurry. As PE has told us, there is more to this than meets the eye. Not that making a double-run is that hard, mind-you, but there are so many variables involved that it is hard to be able to tell what you might be doing. Eventually, though, over the long term it is probably the way forward.


Silver plating is always a nuisance to keep in mind. Happens with glass stopcock burets, too. It's important to keep things rinsed out.

I noticed the buildup after my last double run. I've made three. Two worked, in that I got a working emulsion although it wasn't anything special. One was an outright failure, except I can use it for coating practice. Fortunately, they were all quite small. The needle should clean out easily enough, and if it doesn't, they are pretty inexpensive.


I assume the reason to go with such elaborate tools as hypodermic needles is the hope that they will give you extreme precision

No, not really. I was looking for two things, a smaller orifice to help slow down the flow rate thereby making it easier to add reactants over, say, a 20 minute period in a relatively constant stream. And second, as a way to bring the entry point of the reactants into proximity for mixing purposes. The first they achieve, the second they do not. The initial idea was to bend the needles to bring them together, but that doesn't work because you cannot bend them, or at least not easily without breaking them. So the idea switched to using tubing. I think Chris' idea is better than mine, though.


There are adapters made that are female luer-lok to tubing and tubing to male luer-lok.

Will have to look for this sort of tubing. Sounds like a solution.


... and standard tubing goes over a Luer male connector on a syringe and can be cut to any length and clipped in any position.

Another possible solution but will have to find tubing of the right size. I would guess it's available but never looked.

Things on the photography front at my house have had to take a back seat lately. My available time has mostly been spent playing with the Mamiya 645 so have a little time to figure out the next steps.

-- Jason

kb3lms
01-29-2013, 02:18 PM
There are adapters made that are female luer-lok to tubing and tubing to male luer-lok.

Had a minute this afternoon to look for these. Search "Luer Fitting" on Amazon or eBay. There's all kinds available with barbs for all kinds of tubing.

Thanks for the tip, Joe

Photo Engineer
01-29-2013, 04:27 PM
A few comments are in order here.

Mixing problems go way way up with RS (Run Salt - or Double Run) emulsion makes because the rate, position etc, become more critical. As a note here, with SR and SRAD, I have found little effect on the position of the entry point. With RS makes there is a problem.

We used tubing. We had a plate with holes in it that the tubing went into, and this positioned them at the right place. For back pressure, we used glass or metal constrictors (like the tips on all plastic syringes with a feeding tip on them). These constrictors evened out the flow. There is a demo of this on the second DVD that I made, but it is very simple.

Baffles were used to INCREASE turbulence, and we did NOT want to decrease turbulence. Go back to my toothpaste example and you will see what I mean, or look at the mixer photos I posted here about a year ago.

PE