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Photo Engineer
05-22-2010, 11:06 PM
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

hrst
05-23-2010, 02:03 PM
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?

Photo Engineer
05-23-2010, 02:40 PM
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

hrst
05-23-2010, 02:58 PM
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.

Photo Engineer
05-23-2010, 03:02 PM
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

Kirk Keyes
05-23-2010, 03:26 PM
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.

Photo Engineer
05-23-2010, 03:40 PM
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/product_view.asp?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

alexhill
05-23-2010, 08:14 PM
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.

Photo Engineer
05-23-2010, 11:09 PM
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

Kirk Keyes
05-23-2010, 11:52 PM
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.

wildbillbugman
05-24-2010, 12:02 AM
Kirk,
Here in the Inland Empire one cannot purchase hypodermic needles without a prescrition. Except at many public parks. You need? I get!
Bill

Hexavalent
05-24-2010, 12:08 AM
Kirk,
Here in the Inland Empire one cannot purchase hypodermic needles without a prescrition. Except at many public parks. You need? I get!
Bill

Great. Name the film HIV+ :o

-Ian

Athiril
05-24-2010, 12:34 AM
"I cannot buy syringes with needles in the USA without a prescription from a Doctor."

Wow, I got a whole bunch just sitting here, I find them useful for separating solutions or taking up small amounts of chemical rather than trying to pour into a 10ml graduate cylinder.

Might I suggest looking on eBay for printer ink refill bottles that usually come with syringes + needles ;) I think mine came from HK (you may want to adapt the tubing to a needle and araldite it in rather than use the syringe+plunger).

I can mail you some if you want.

Perhaps we could start some sort of fund raiser?



Anyway, PE, it might be cheaper in the long run from not having to use so much raw material if you get someone to make this stuff (hardware) for you? Someone that builds complex stuff out of their house.. my uncle was building prototype magnetic mineral separating machines for the mining industry out of his home workshop (though there were a few indicents of magnets exploding and putting holes through tin walls, or exploding and collapsing back in on themsleves :P)

What kind of pump are you using? Might I suggest a cavity pump?

mike c
05-24-2010, 12:41 AM
Had a program here in LA were you could get the needles for free with one catch,you had to be a drug addict.Go figure.

Photo Engineer
05-24-2010, 09:32 AM
..........

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;

I agree. The Masterflex, which I have, is probably the most popular in many circles and is the pump we used for a lot of things at EK, so I felt confident in it.

The problem is that this formula is probably wrong for this scale and that formulas made at this scale must be very carefully chosen for all characteristics including flow rate or pumpability, if that is to be done. A three hour run is not possible without pumps.

Therefore, I think I will move on to an emulsion with a higher flow rate or a shorter run time or both.

As for getting someone to build things for me, that is what I did with the coating blades and it just did not work out in the long run! Plastic joints leak or fall apart in these hot solutions, or they absorb chemicals. Stainless Steel is expensive and hard to work with... etc....

And, if I get too specialized, then who can do this in a home darkroom? After all, that is one goal of my work.

Thanks for all of the suggestions though.

PE

hrst
05-24-2010, 09:55 AM
I've been seriously thinking the motor-controlled syringe concept and how I could improve the concept to an acceptable point and then make a cheap prototype. I have the experience and ability to make all the required control electronics and software (to have a feedback from the measured vAg, for example), and the mechanics is not impossible either if I can keep it simple. However, this all will take time as I have many other projects going on. But, if I ever get a working prototype under construction, I'll be in contact with you, PE!

Basically I would need three solutions - AgNo3 solution, Br solution and I solution, correct? Allocating three syringes for every solution would make total of 9 syringes. They would be controlled by linear stepper motors that cost about 15 USD each. IIRC the ones I've been planning to buy can be controlled by 0.024 mm steps. With small syringes (down to 1 ml or even smaller, if needed) you could get very slow and steady stream. OTOH, 50 ml is the biggest easily-available cheap syringe. I have 25 of them and they cost about 1-2 USD each. With three syringes per solution, for example, 5 ml, 20 ml, 50 ml, you could get total 75 ml of each solution with very flexible flow rate range. Syringes would be connected to very thin tubing, e.g. 0.6 mm, 1.0 mm, 1.5 mm respectively. You would lose only a ml or so of the solutions in this short tubing. If there is problem with solutions dripping out instead of spraying, very small nozzles could be made at the end of the tubes.

This won't scale up much, but I bet it could be made to work with small volumes (0,5 liter or less of emulsion?) quite well, but it would take time. And I don't have the necessary know-how in the modern emulsion making, which is a problem. I would be very thankful if you, PE, could post some examples of the exact pumping ramps/curves, so I could get a better idea what's needed.

Athiril
05-24-2010, 11:04 AM
Rather than a pump, how about using a gas pressure system with a pressure regulator via the needle? It should be pretty consistent, air or inert gas would do it I'd imagne?

I imagine you could use a decent air-compressor also.

IE: Something along the lines of my awesome CAD schematic here :)
http://i50.tinypic.com/53tjsw.png

Photo Engineer
05-24-2010, 11:13 AM
Kodak used syringe systems for some flows due to the limitations of pumps. The ratio of high to low flow rates required many pumps. This ratio is called the "turndown ratio". There was a very long series of threads on various methods for doing this and Bob Mazzullo contributed a lot of good ideas and drawings.

The air or gas driven system is good but does require a flow meter to get enough precision, as well as a regulator to add vAg control. Feedback is difficult.

As with most emulsions, you will need a minimum of about 5 delivery systems. AgA, AgB, XA, XB and XC. These represent 2 concentrations of silver and two of 2 different salts. To make my 1 L emulsion, I delivered 300 ml of silver and 300 ml of salts (approx) to a 300 ml starting kettle. So, consider that your delivery systems will need to contain up to 300 ml.

PE

Athiril
05-24-2010, 11:18 AM
Hmmm, PE, wouldn't a pressure regulator at the end of your setup allow you to increase pump output and restrict it with the regulator, and hence give you a regulated consistent output?

Photo Engineer
05-24-2010, 12:18 PM
Hmmm, PE, wouldn't a pressure regulator at the end of your setup allow you to increase pump output and restrict it with the regulator, and hence give you a regulated consistent output?

Yes, however precision flow meters in this range are very expensive, and many of them use brass or copper fittings which corrode in the presence of AgNO3. They usually run in the range of Liters / minute or CC/min, in ranges far above what I use.

At EK, I had the complete catalog of one of the large companies and had their precision flow meter kit with dozens of them in the kit. I used them for many projects, but finally dissolved a set with the wrong chemistry. I had to reorder several very expensive meters and learned that you need stainless points and balls. Some of mine were Dwyer IIRC.

This need for stainless increases the cost.

PE