Ron, your emulsion has some problems. The emulsion is not even sulfur sensitized, so the speed and contrast are too low to be useful for most applications. Another problem is that the supersaturation is too high with your 3M AgNO3 jet, unless you can somehow jet it through very narrow nozzle with high pressure (this technique is disclosed in recent Fuji patent, issued in 2005). Also, pure chloride emulsion is not very useful. Most modern chloride emulsions contain 1-10% bromide and/or 0.1-1% iodide. Kodak patents often use AgCl core, AgClI shell and cover them with AgCl. Fuji patents often introduce AgBr shell inside AgClI layer. I've followed those inventions (but with different dopants) and they work beautifully.
The emulsion is best stabilized with PMT (and TAI, especially if sulfur sensitized). Optimal amount of PMT can also increase speed. If the emulsion is to be kept for some time, the emulsion should incorporate a suitable biocide as well.
Originally Posted by Photo Engineer
Dogma and Karma
A few comments...
Originally Posted by Ryuji
Ryuji, I belive this was Dr. Kahn formula, not Ron's.
Did you actually make this one yourself and thus speak from experience with this formula?
I see many real and potential problems with this formula myself, but I didn't jump up and tell Dr. Kahn this when we met just after Dr. James died at the close of the last century.
(Any idea why I didn't?)
There are good pure chloride emulsions too Ryuji.
The most modern photographic material contains no Silver halides at all.
I doubt TAI is the optimal stabilizer for this emulsion.
I actually discussed problems with that student lab formula with Dr Kahn and he told me that the formula was something he inherited when he took over that course, and continued to use it because it's good enough for the student lab. He is not interested in teaching how to make practically useful emulsions in such setting anyway.
I also don't agree with your comments on more technical matters.
Originally Posted by Baryta
Ryuji; I had lunch with Bruce a few weeks ago and I am fully aware of the source of the emulsion and the problems associated with it. We discussed this emulsion thoroughly. Bruce is an expert on chloride emulsions and finishing. Since we are both former EK engineers, we could have a free ranging discussion without the restrictions we have here.
I showed him my pictures and the comparisons to Ilford Multigrade IV at contrast grade 2 to illustrate the tone scale that I am getting. Of course, he is not endorsing anything I have done, but he is fully aware of it.
I have worked hard to fix the problems as I saw them (and as you and I discussed before), but even as-is the formula is a grade 2 Azo speed (contact speed), black toned formula. It is quite nice except for the pepper grain which we discussed before as well. I have fixed that.
For an azo speed grade 2 paper, it performs very well. I have since gotten ~grade 1 and grade 3 and grade 4 from it as well, as stated in another thread. I can do this through modifications in the making method.
Just FYI, I do indeed use a small injector orifice at high pressure. That is well known and has been for years. How else do you think a large quantity of concentrated AgNO3 can be delivered in a small amount of time? That seems to be obvious to me.
In fact, when I was doing real work, I remember blowing a seal because I let the pressure go too high on a make. Now that was a mess.
It seems that I must agree with Baryta regarding his comments on the technical details of this emulsion. PMT slows it down, and keeping is good without TAI for my purposes, so I have never even tried adding it. I have also achieved slow enlarger speed from it using some modifications you said in another message were not useful, but which I knew would work. I have spectrally sensitzed it as well.
For preservative (biocide), if needed, I suggest using Thymol, 10%, about 0.1 ml / 100 ml of emulsion. So far it keeps well for me for a few months.
So, I have made this formula over 10 times, each one of the first 7 being improvements, and now I am at a stable formula which I have repeated about 3 times and which is the basis for further experiments. It is the basis for an AgCl, and AgClBr, and an AgClI. They are all simple and intended for the home hobbyist.
If they bother you, just remember that they work.
Ron, I'm not bothered by your work. Your approach to emulsion making is 1920-like and I could immediately point out a LOT of things to improve, some of which I already posted.
The method of mixing silver and halide using high velocity linear flows in a closed container without rotational agitation is new on patent literature. It only appears in US Patent in 2005. As discussed in that patent, the mixing is highly efficient as a premixer to use before the kettle during growth stage to keep supersaturation low. The one you are talking about is known from 1960s. There is nothing new there, and it helps little in terms of avoiding area of very high supersaturation in the kettle.
Any emulsion maker knowledgeable in chloride emulsion would know that the optimal amount PMT can INCREASE speed of <100> bounded AgCl and AgClBr emulsions (S sensitized). Tani figured out the mechanism in 70s and he published this results in many papers and also in his book, so it's very well known. TAI is most effectively used in addition to stabilize S sensitized emulsions. You might never felt the need of using TAI because you don't give optimal S or S+Au digestion.
Even in <111> bounded grains, a certain small amount of PMT can be added without lowering speed.
For record, I usually make far more than 10 batches to test formulae and find optimal parameters. Most emulsions are subdivided into several portions and they are digested in different conditions to find most useful conditions.
Originally Posted by Photo Engineer
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Ryuji, the details of mixing during making of emulsions is a subject off-limits to me for this discussion.
As for the mention of injecting silver though, I do use relatively high pressure with short times and high mixing rates. This is known in the literature and there have been patents and discussions about it.
You may be interested in the novel methodology suggested by Wey and Whiteley in their US patent. I'm sorry but I don't have the reference at hand. I'll post it later if I can find the number.
Your published approach is also from the same era and looks much like Kodak publication AJ-12 as I said in another post. You surely have more modern versions but I have not seen them, and I wouldn't think of commenting on them without trying them out.
I make my emulsions in 120 or 220 gram batches and divide them into 30 g portions for easy breakdown for finish and doctoring experiments. So, for 10 makes of even 120 grams, this is 30 experiments and for 220 gram makes that is 60 experiments.
Wey's work is classic. I've read the original reports and I'm familiar with his work, as far as published results are concerned.
I'm happy to post one of t-grain emulsion formula if you have a triple jet apparatus and suitable gelatins. Here's whet I remember top off my head right now.
I use oxidized phthalated gelatin in kettle at 35C for nucleation, and bring the temperature up to 70C for ripening, then growth. Just before and during growth stage phthalated gelatin is added in addition to Ag and X. The third jet controls the iodide shell and incorporation of dopants. Ripener is used for negative emulsions during the growth stage.
The Ag and X jets in nucleation stage is 0.1M and 0.2M, respectively, while pBr is 1.5 and gelatin in the kettle is 0.5%. The jets are 1M and 1.2M during growth, at pBr of 1.0, and gelatin in the kettle is 2.0%. If pBr is too low, contrast lowers. The kind of gelatin, as well as the gel concentration have large influence on aspect ratio of t-grains.
After growth, I desalt by coagulation method. Digest S for paper, S+Au for negative (R sensitization is done in the interior of the grains for negative emulsions). Add sensitizing dye and allow time for adsorption at this stage. Then stabilize with TAI, PMT and pBr, pH adjustment. Add a biocide and cool for storage.
For negative emulsions I blend 3 emulsions after all above steps are performed. These 3 emulsions receive different growth and digestion steps, but they are otherwise similar.
Originally Posted by Photo Engineer
Ryuji, I'm sure it is a fine emulsion, but very complex. There are simpler and better ways to do what you are doing that are much more modern. There are also much more complicated and better ways to do this as well. It depends on your final aim.
If you look at the figure posted on Bruce Kahn's web site, you may get an idea of how complex the plumbing and electronics can get for a modern making station. That figure of his of course, is for a dual jet emulsion. In reality there are many more addition stations than even you mention above and more than he depicts in the 'real world'. Several can be in action at one time.
I'm also surprised at some of the steps you leave out and the methodology of adding ripener. It will work, I'm sure, but again I would do it differently.
The pBr is really pI since Iodide is present, so wouldn't it be better to report pAg? And how do you control pAg or whatever you measure? If the pAg varies, it may be due to iodide or bromide depending on addition method and unintentional solution flow rate fluctuations. What is your reference electrode plated with? Or is it plated at all?
Be careful of placement of inlet orifices. Positioning errors can give different pAg values depending on inlet spacing and mixer rate as well as electrode type. This emulsion will probably be difficult to scale up or down due to mixing problems. Just as an offhand suggestion you may want to make a 2x batch or a 4x batch to see if it still works.
The use of Phthalated gelatin will reduce the maximum grain size attainable at any given temperature, IIRC, but then it has been quite a while since anyone used that at Kodak or Fuji. I think phthalated gelatin was abandoned before T-grain technology.
I'm surprised you are not doing UF washing by now.
I see no provision for acid or base adjustment during the make. Of course, using phthalated gelatin this is impossible to implement, and that is too bad, as it would improve the emulsion in all probability. This is one of the major advantages of UF washing and one of the major disadvantages of using PA gelatin. There is a way around it, but you didn't mention it, so I guess you don't want to use acid and base adjusts.
I am avoiding T-grains, as they look and act too modern. I'm working with K-Grain technology.
Ron, when are you going to stop talking nonesense about things you really don't understand in an effort to imply you are always right and the smartest on the internet? I'm sick of your arbitrary stories you make up when you don't know real answers already exist and they are known to others. What's ironic is that much of the real answers were worked out by people from Kodak Research Labs in Rochester, where you repeatedly claim that you know most of findings in both public and secrecy.
Oxidized gelatin and phthalated gelatin are useful colloids in preparation of tabular grains of high aspect ratio. Both of these gelatins have less restraining action and indeed make larger grains while other conditions are fixed and when compared to regular inert gelatin, so what you said about grain size does not make sense at all. This is the kind of work done by Maskasky at Kodak Research Lab and I thought you knew all about what was done at the KRL. It's surprising that you didn't know that.
You are very confused about pBr, pI and pAg. They are all related to each other by a set of equations. In modern negative emulsions iodide is added in a highly concentrated form in a rather brief time as one of the shell layers. The core is bromide, and the outermost shell is also bromide. During nucleation there is usually no iodide at all, as presence thereof results in lower aspect ratio. pBr is most important in this stage to maximize the probability that a crystal will possess two twinned planes. Ripening is used to remove non-t-grains before growing the crystals. A lot of particular aspects of my emulsion making are designed so that the emulsion is mostly consisting of one kind of crystal habit.
Originally Posted by Photo Engineer
Ryuji, oxidized gelatin yes, PA gelatin not much at all. It prevents some operations that requre acid - base shifts during the make. If used, it is at low conversion levels to prevent acid - base shift related problems.
The measure of pX or pAg is not accurate enough for this type of work. Iodide is usually run in slaved to silver and bromide is run in control with proper control equipment and proper measuring devices with appropriate electrodes. Somtimes other methods are used to control halide addition.
If your emulsion is a T-grain, I hope it avoids all current patents for both making technology and aspect ratio. Both are patented.
Yes, I am aware of the work of Maskasky, Daubendiek, Marchetti, Perry, Wey and Whiteley to name a few. I simply cannot discuss it in detail.
And, if my work does not bother you then why the continuation of this thread? Why start it at all? Why pick at my work? I feel that you are doing good work - albeit complex, and have no issues with what you are doing. I simply have different goals than you do, and know a lot that I cannot disclose and so walk a knife edge in my discourse here and in the work I do in my own darkroom.
I could write several paragraphs on measurment of pAg and variants, and several on mixing, but these are really off-limits. I could do the same for addition methodology, again it is off limits. I could discourse for hours on mathematical modeling of pAg with different halides, another off limit subject. How about emulsion scaling models. I know a lot about that as well. All of this is off limits as far as I'm concerned.
As for techniques, yes there are better emulsions but I choose to pick simple ones. Yes, there are a lot of ways to sensitize, and I have done most of them here or at Kodak. My raw and sensitized emulsions do very well. Out of the can the AgBrI has a raw speed of ISO 25. After sulfur sensitization and spectral sensitization I will probably get a lot more, but lose some to antifogging / stabilization, and addition of acutance dyes for sharpness. I hope for ISO 25 but may get as high as 100. That is my hope. I hope to do it with simple emulsions with no fancy equipment and no long making or sensitization steps.
I commend you for your diligent and good work. I hope that people are interested in it and I hope you can avoid patent infringement. I'm sure that there will be people interested in your work. I hope that perhaps some people will be interested in my work as well.
My comments above regarding your T-grain make were intended to show merely that there are many possible ways to do the same thing. T-grains are made at all major manufacturers plants and each manufacturer uses different methodology. I did not intend those comments to be taken as negative in any way. After all, if it works, it works.