PE, one quick question about hypo sensitization:
Do you think it's necessary to stir the emulsion while giving heat treatment, or should standing in closed container sitting in water bath do?
It should be stirred. A closed container is optional, only to minimize evaporation if you wish.
I have a quick query that I hope you can help explain.
The speed (ASA) of hrst's emulsion is very high....higher than indicated in your post "a real formula"
Is this most likely due to the silver addition method and pig gelatine??
From the OP, it seems that they got ISO 25. I get ISO 40 - 80 from my emulsion after sulfur sensitization. So, I would say that their modifications may have given higher speed to start with and that they may have very high speed after sulfur sensitization.
I cannot really say though. I can just hope that they can repeat it and that they have continued good results.
It may be all thanks to "active" gelatin. We'll try hypo sensitization tomorrow. I'm very happy if we can get one stop more without fogging.
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Depending on conditions, you may get 2 or 3 stops. You can get more than that with the addition of gold. You can restrain fog with tetra aza indene.
Your results are superb!
Next time you make a batch would it be possible to document your exact process so that we can try to "walk in your footsteps"?
What brand pig gelatine are you using?
Originally Posted by hrst
Originally Posted by Photo Engineer
I have exact notes. They are at darkroom, I can post them here soon.
Gelatine is a traditional, standard food gelatin in sheet form of a local Finnish brand. It's probably imported from somewhere, though. http://www.meira.fi/maustaminen/leiv.../liivatelehti/ . All it says it's made of pig skin. But maybe the thiourea component that causes the sensitization vary brand-to-brand and also batch-to-batch. But I think that sheets have lower possibility of having extra additives than powdered products. I might be wrong.
The reason why I'm using food grade gelatin is "just for fun" and I want to know if it is possible; and I like the good availability and independence from specialty products. And it seems to be possible. But probably the easiest way would be to use photograde gelatin, unless you have the same motives as I .
Last edited by hrst; 07-03-2010 at 09:15 PM. Click to view previous post history.
Notes of this emulsion
100 ml deionized water
NaBr 11,41 g (=0,1109 mol)
KI 0,60 g
Gelatine (as discussed before) 2,50 g
Erythrosine 150 mg/mol of silver -> 11,475 mg, or 1,15 ml as 1% wt/wt solution
40 ml deionized water
Silver nitrate (self-made) 13,00 g (=0,0765 mol)
25% Ammonium Hydroxide added at 42 deg C. Solution cleared at 12 ml.
Filtered B with 5 um filter paper. There was quite a lot of precipitate/gunk not visible in the solution but well visible in the filter paper, probably due to home-made silver nitrate.
A heated to 42 deg C and stirred with magnetic stirrer at 1000 RPM.
Silver nitrate solution put into two syringes; 1 ml and 50 ml. Tempered them to 42C in water bath.
Addition with syringes, stirring at 1000 RPM all the time.
2% (1 ml) of B added in 5 seconds
waiting for 45 seconds
49% (~25 ml) added in 3'20"
waiting for 8 minutes
49% (~25 ml) added in 4'00"
waiting for 10 minutes
added 1.0 g gelatin (as I remembered PE saying that extra gelatin during digestion might prevent fog!)
waiting for 5 minutes
This was the addition sequence I planned, HOWEVER it wasn't so easy to inject at constant speed in the dark. I had timers for additions so the timing was exact, but the addition rates (injection speeds) were something like this:
Stirred in room temperature water bath for 3-5 minutes, to cool down a bit, and then put to lighttight container for two hours at room temp.
Room temp was 25,5 deg C.
After two hours, temperature back to 42 with constant stirring on magnetic stirrer. Added 15 g gelatin. Neutralized ammonium hydroxide with battery acid (H2SO4). Destination pH was 6.0 but we got 5.6. Didn't want to mess around with that anymore so we decided it's ok. I didn't write down the exact amount of acid needed but it was around 6 ml.
Chilled with cool water bath and put in the fridge until gelled.
Pushed into noodles using an "innovative garlic press" like in this picture: http://www.4garlic.com/images/hands_4939.jpg. Dropped the noodles in Jobo tank filled with 4 deg C deionized water. Put the Jobo tank in water bath with ice cubes. First two or three water changes quite quickly, then standing for longer, agitating gently. Temperature was 3...5 deg C all the time. Kept the water in the fridge.
It was maybe after 30 minutes we decided to take a conductivity reading of the wash water for the first time. This wash water was in tank for 10 minutes. It has to soak in the tank with noodles for long enough so that the salt concentrations in emulsion and in wash water get near equilibirium so that the reading of water should be quite near of the concentration in noodles. Anyway, our meter showed 600 kOhm, whereas it shows 800 kOhm for deionized water, 400 kOhm for 0,030 g/l NaBr and 200 kOhm for 0,200 g/l NaBr. At this point we were surprised it washed so quickly and continued washing with 0,100 g/l NaBr water for 10 or 20 minutes.
Then, drained the water from the noodles and dried them to microfiber cloth (that was washed well with water and then deionized water). Put the noodles in fridge.
25 ml of emulsion
5 drops Agepon
0,15 g sorbitol
0,5 ml glyoxal
Blade gap: 150 um
Dried for a day
Complete clearing time in fixer: 120 seconds
Developer: XTOL 1+1
Temperature: 24 deg C
Optimal dev time: around 4...5 minutes
Dmax: Quite good
ISO compared to Agfa APX 100 in XTOL1+1 for 7 min at 24C: 25
Usable logH range: about 8 f/stops.
Coating flaked off from the base - this was acetate, so our subbing went somehow wrong this time.
Then, next coating with corona discharged PET. The results are in the first post.
Hope this helps!
Last edited by hrst; 07-04-2010 at 03:50 AM. Click to view previous post history.