Photo Engineer said:Commercial emulsions often remain unsold on the shelf for a long time. They are not high volume items. Therefore, they may deteriorate with time. IDK, I have avoided using them.
PE
doughowk said:A wealth of info can be found in Silver Gelatin:A User's Guide to Liquid Photographic Emulsions
glbeas said:So how do you calculate the moles into actual weights and measures?
doughowk said:A wealth of info can be found in Silver Gelatin:A User's Guide to Liquid Photographic Emulsions
Ole said:That is basic chemistry, this is more advancd labwork.
glbeas said:So how do you calculate the moles into actual weights and measures?
Photo Engineer said:It is possible to make your own liquid emulsions in the darkroom in about 45 minutes total time with only 7 chemicals. The results will be between slow enlarger and contact speed and will have contrast grades of about 2 or lower. This includes hardening agents and spreading agents.
Formulas for the emulsion are posted on the net or available from participants in this or other forums.
With additional work and at least one more chemical, you can achieve up to ISO 25 and ortho sensitivity. These formulas are not posted or currently available, but I understand that they may be in the not so distant future.
Your biggest problems with the commercial and home grown emulsions alike will be adhesion to the substrate, spreading (coating uniformly) and hardening. Commercial emulsions often remain unsold on the shelf for a long time. They are not high volume items. Therefore, they may deteriorate with time. IDK, I have avoided using them.
PE
Photo Engineer said:Here it is in English then:
To 90 grams of distilled water, add 5 grams of photo grade gelatin and bring it to 40 deg C. Stir constantly. When dissolved and there are no floaters of gelatin, add 3.51 grams of reagent grade Sodium Chloride (NaCl). (I find dissolving the gelatin first is best)
Note, stirring should be continuous, and strong, but should not whip air into the gelatin salt mixture. Don't overdo the stirring, but don't underdo it either. Overdoing it will give you bubbles, and underdoing it will lead to a bad emulsion with foggy large grains.
In another container, dissolve 5.1 grams of Silver Nitrate (AgNO3) in 10 ml of distilled water.
Bring the gelatin and salt solution to 60 deg C with stirring. Turn out the room lights and turn on a red or yellow safelight, and then add the 10 ml of silver nitrate to the salt solution as you continue stirring.
Set a timer for 5 minutes and hold the mixture at 60 deg C for 5 minutes then place in a light tight container and place in the refrigerator. This will keep for about 1 month with no deterioration, perhaps longer.
You can coat this on about any surface with a paint brush if you remelt it at 40 deg C. I suggest a good camels hair brush with loose bristles removed.
If you have trouble with even coating, add a drop or two of photoflo 200 to the melted emulsion. If you need hardening, add a few drops of 10% chrome alum to the melted emulsion. If you add any hardener, the emulsion must be used as soon as possible or it will set up to a putty like mass.
Exposure time will typically be in the contact paper range. I've used about 3 seconds to normal room light. You should get a good black image with a contrast of about 2.
How is that?
PE
Ryuji said:Ron, your emulsion has some problems.
Also, pure chloride emulsion is not very useful. Most modern chloride emulsions contain 1-10% bromide and/or 0.1-1% iodide.
The emulsion is best stabilized with PMT (and TAI, especially if sulfur sensitized).
Baryta said:A few comments...
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.
So what?
I doubt TAI is the optimal stabilizer for this emulsion.
Baryta
Photo Engineer said: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.
PE
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