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hrst
07-02-2010, 06:01 AM
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?

Photo Engineer
07-02-2010, 08:50 AM
It should be stirred. A closed container is optional, only to minimize evaporation if you wish.

PE

Emulsion
07-03-2010, 12:50 AM
PE

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??

Many Thanks,
Emulsion.

Photo Engineer
07-03-2010, 08:49 AM
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.

PE

hrst
07-03-2010, 07:40 PM
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.

Photo Engineer
07-03-2010, 08:05 PM
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.

PE

Emulsion
07-03-2010, 08:10 PM
Hi hrst,

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?

Many Thanks
Emulsion.



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.

Emulsion
07-03-2010, 08:13 PM
Thanks PE.


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.

PE

hrst
07-03-2010, 09:09 PM
Emulsion,

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/leivonta/leivonta-aineet/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 ;).

hrst
07-04-2010, 03:43 AM
A
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

B
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:

http://www.apug.org/forums/attachment.php?attachmentid=19985&stc=1&d=1278231843

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.

First coating:
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
Dmin: Good+
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!

Emulsion
07-04-2010, 08:21 AM
hrst,

Thankyou very much for that wonderful post with your detailed procedure.

Your scientific approach is really appreciated!

Regarding the gelatine, I like your approach of using food grade product. It is far easier to obtain at a reasonable price.

Emulsion

Photo Engineer
07-04-2010, 10:52 AM
Very nice.

Some observations...

At that level of gelatin, I would imagine that the final melt would be very viscous or that the gelatin has a low Bloom Index making it inherently lower in viscosity. Of course, this does not take into account expansion during washing which I cannot judge.

And, that addition profile can be deleterious to the proper grain growth. The middle curve should either be flat, with the next addition starting where that one left off, or it should rise with the next one starting where that left off. This is to take into account the growing crystal size. You accelerate addition to try to match the rate of growth.

I might add that this is very close to an emulsion currently in the book.

PE

hrst
07-05-2010, 02:16 PM
Today we took a look at the commercial corona treatment unit again and made some... ahem... measurements. I don't know if I'm allowed to give exact information about the unit such as name, but I can now give.... an educated guess for starting point for corona treatment: simple sine wave AC without any DC offset, Urms = around 2.5 kV, with frequency of about 20...30 kHz. As it is AC without offset, it doesn't have a problem of correct polarity ;). I'm sorry but I probably can't give more exact information, but I'll restart my own experiments quite soon and I can give specific information about them...

I still probably have some work with correct electrode design, but my problem with my earlier experiments is becoming clear to me; I have been using DC voltage, or too high DC offset voltage when using AC. All I got was huge static charge. Corona was on all the time. But the key to surface treatment seems to be in the quick toggling of corona on and off, that is, AC voltage with high enough frequency.

dyetransfer
07-05-2010, 04:18 PM
I still probably have some work with correct electrode design, but my problem with my earlier experiments is becoming clear to me; I have been using DC voltage, or too high DC offset voltage when using AC. All I got was huge static charge. Corona was on all the time. But the key to surface treatment seems to be in the quick toggling of corona on and off, that is, AC voltage with high enough frequency.

Hi -

I once worked on a high voltage amplifier, which ran at about 20 khz at 20,000 V. I used to light my cigarettes from quite a distance with that rig. The arc had strange properties - if you put you finger near it, it would arc over, but it would just burn the callus of your finger, it wouldn't go deep. I think that HV HF is conducted only on the surface. Not sure if that has anything to do with your polyester prep, but it is an interesting effect. In some ways High Freq HV is much safer than DC HV (which can cause a lock on situation while you just sit there frying)

Regards - Jim Browning

Kirk Keyes
07-06-2010, 11:27 AM
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.

What kind of conductivity meter are you using. Typically, conductivity is read in uS/cm (that's "microsiemens per centimeter) as the resistance increases as the distance between the electrodes increases.

Keep in mind a Siemen (S) is equal to a Mho, which is 1/Ohm. Some people forget about the distance aspect and omit it. Also, really good DI water should read "18 MOhm" or higher.

hrst
07-06-2010, 01:56 PM
I just used a regular digital multimeter and made a simple metering electrode with a fixed distance that wasn't selected by any correct means. My point was just to get some quick relative numbers that can be compared against each other.

hrst
07-06-2010, 02:07 PM
Sensitization experiment:

We added hypo at 100 mg/mol and stirred at 60 deg C, getting and coating samples every 10 minutes.

After 10 min, there was a little fog. After 20 min, quite a bit, after 30 min, almost completely foggy, and after 40 min, completely fogged.

However, the results at 10 and 20 min, however a bit fogged, were very poor when we exposed Stouffer scale on them. We found that the speed actually DROPPED (which is quite surprising) and contrast and DMAX seems to be dropping as well. The coatings were quite poor quality due to small samples and that may play a part in the results, but still I'm surprised. The best one in the series is the first one which we made before adding hypo and before reaching 60 deg. C. It hasn't changed at all during storage for 14 days. It was also nice to see that is survived the process quite well even without any hardener and with only one hour of drying time, assisted with hair dryer. I can post curves from it quite soon. Our approximation of ISO 25 stays so. Sensitization was a failure. We could try it again with less hypo or with no hypo at all, as the residual sulfur compounds in gelatin might do it with the heat treatment only.

Is there a chance that 14 days in refrigerator might render the emulsion to non-sensitizable, even though it's perfectly ok otherwise?

Photo Engineer
07-06-2010, 02:14 PM
I think that your emulsion is coarser grained than mine. The use of hypo is a surface phenomenon and therefore as size increases, amount should decrease. By the results you report, I might suggest going to 25 mg/mole.

PE

hrst
07-06-2010, 04:00 PM
Curves.
Without hypo sensitization which was failure. Test coating was a bit uneven which may affect results a bit. Test exposure was 1 stop more than for APX100, (so if they matched, it would be ISO50.)

Epson V700 scanner, profiled with a Stouffer scale, was used as a densitometer. X axis is not actual lux-second scale but should be considered relative.

Density readings may be a bit off, too. They sound a bit low to me. But the curve shape and logH range are interesting. Contrast is quite close to APX100.

But, despite having the first visible step at ISO25 compared to APX100, when looking with bare eye, it's probably better shot at EI16 or EI12.5 due to curve shape.

dwross
07-09-2010, 09:05 AM
Why did you decide to go with the higher temp? 60C is mighty hot for an ammoniacal emulsion. I've never seem it that high in the literature, and the one time I let the temperature get away from me when I got distracted, the emulsion was horrible (flat and slow.) I keep to 40-45C.

And, for what it's worth from my experience: I don't use hypo sensitization, but I do add gold to the washed noodles during the last ripening. I've had noodles in the frig for three weeks (without preservative) and things went fine.

d