• Welcome to Photrio!
    Registration is fast and free. Join today to unlock search, see fewer ads, and access all forum features.
    Click here to sign up

Our newest results.

Kirk Keyes said:
I think PT Barnum said that once.
;^)
Click to expand...

He said "You can please some of the people some of the time but not all of the people all of the time!"

Or maybe it was someone else. IDK. I am unsure because I don't want to displease anyone.

PE
 
Kirk, to do that would involve extrapolation, correct?

Which method of extrapolation would you consider suitable for this data?

Similar data I have seen before has always been on logarithmic graph paper... and covered the full range of interest; if you find your Excell sheet perhaps it can be fleshed out a bit without the need for extrapolation....

A similar version:
You may fool all the people some of the time,
you can even fool some of the people all of the
time, but you cannot fool all of the people all the time.
 
Last edited by a moderator:
Ray;

This mV chart is limited by the pAg scale and by the PKSPs of the halides. Therefore it asymptotically approaches a limit at each end. The low limit is AgI at about -300 or more mv and the upper limit is AgCl at about +250 mv. Mixes are in between. A log scale would be linear in shape but not in concentration as is obvious and may confuse some people. A non-log scale is not linear as shown in my example above.

Extrapolation is not necessary as the curve I showed is entirely calculated and is therefore an extrapolation itself requiring only more data and "running time" to extend the curve. But, this serves no purpose in most cases as we only need to know that about 0.1 g/l of NaBr or a vAg of about -50 to -70 mv at 40 deg C is optimum for keeping and fog prevention. This comes from the basic properties of Silver Halides.

The same can be said for the final pH of an emulsion BTW. However, in this case it controls speed and contrast instead of fog and keeping.

PE
 
Last edited by a moderator:
Update:

I managed to build a prototype of a 35mm perforator. It wasn't impossible at all, in fact I'm surprised I made it in one night (that was an all-nighter, though). Perforations look quite awful, but IT WORKS, and I believe it's usable because the requirements are not so high in still photography. Perforating two holes at a time is tedious so I started to automate it. I made six large electromagnets that hopefully will be strong enough to punch the holes. I'll post more details later!
 
Ray Rogers said:
cf


???

It looks like the VAg in both quotes (both 0.1 g/l) have different signs...
Click to expand...

I think the first is in reference to bromide and the second is chloride.
 
Ray;

In post #29, which does not reproduce well if quoted, I think you have combined 2 different passages and mixed information. Can you give the post numbers that you used of mine so that I can give the correct or clarified figures?

PE
 
The flow of logic went as follows:
(#1)
#6 === #21 (positive VAg)
#28 (Negatve VAg)
-------------------------------------------
HRST makes a statement about a particular halide conc. in his inital post (#1)
You comment in #6 about positive VAg
and defend this comment in post #21
but switch signs in your post #28 when you mention Negative VAg
-------------------------------------------
(#1)
We used a simple conductivity meter to measure wash water compared to conductivity readings of NaBr solution of 0.030 g/l, and found out that the washing step was quite quick, less than one hour. For final wash, we used NaBr at 0.100 g/l in wash water.

#6
At that concentration of NaBr after the wash,
[this presumably can only refer to the 0.100 g/l NaBr in post #1]
at 10 deg C (a good wash temp), the vAg would be about +37 and at 40 deg C (a good coating temp) it would be about +67 mv. This is a very good position for the final emulsion.
I often aim for about +50 mv.

#21
At 0.1 g/l, the value given above, I assure you that the vAg is positive.

#28
we only need to know that about 0.1 g/l of NaBr or a vAg of about -50 to -70 mv at 40 deg C is optimum for keeping and fog prevention.

==================================================
To simplify:

Why if "a vAg of about -50 to -70 mv at 40 deg C is optimum for keeping and fog prevention would you "often aim for about +50 mv" ?
 
Last edited by a moderator:
Ray, everyone;

My post #28 has a typo in it. The correct final vAg for a washed emulsion should be about +50 to +70 mv at 40 deg C. If you go much higher, the emulsion can fog. This assumes a Bromide emulsion. The value is correspondingly higher for a Chloride and lower for an Iodide.

Sorry for the error. Thanks Ray for a good catch.

PE
 

And the fun, exciting news just keeps coming from y'all! Needless to say, I hope you publish all the details. And not just here. APUG's great, of course, but I think recent conversations show that it shouldn't be the only place information gets placed. As PE pointed out -- it can get GWTW (which I had to google: Gone With the Wind). I tell myself that silver gelatin emulsion research isn't Peace, Equal Rights, or Not-Oil Energy, but it's still important. (Ron, it's really time for you to get something on paper and/or your own website for posterity.)

hrst, I'd love to know more about you. You say 'we' sometimes. Are you part of a team? A student? Is this research part of your graduate work? I have my fingers crossed that it is. You could be at the forefront of some really significant contributions. Anonymity is fine, of course, and for better and for worse, is part of the internet culture (I tried to stay 'gender neutral' until PE outed me) but it would be fun to put some of your great ideas in a personal context.

Denise
www.thelightfarm.com
 
Denise,

I think I could publish the drawings & instructions of a simple perforator for The Light Farm, if it is fine with you! I agree that APUG is a good medium for discussion and blog-like newsflashes, but you're right that a web page is better for "completed" information.

Occasionally I say "we" and occasionally "I". This is because I have a friend who I'm making emulsions with, but he seems to be quite busy (with work and his family) so when he's not available, I make things alone. I live alone so it's easier! I am a BSc, a student of computer science; and my friend is a student of material science, thus having access to some of the labs etc. Both of us work on part-time (and full-time at summer) as research assistants on our corresponding departments. Mainly we have taken advantage of de-ionized water, magnetic hotplate stirrer with temperature feedback control and now the corona treatment unit. My objective, however, is to become independent someday so that I can make this all at home.

This emulsion work is "just for fun" for both of us. I'm afraid it's not that easy to do MSc thesis on emulsion making to the department of computer systems . Although there would be possibilities for computer automation, but I already have a subject for my MSc that relates to my (paid) work at the department, design of the integrated circuits. My BSc thesis was about the Motion Picture laboratory (pdf is in Finnish but has an English abstract) I'm building but it seems that lab will take some more years to complete

We/I do the emulsion work at our university's photography club's darkroom which is small but I like the atmosphere.
 
 
hrst said:
This emulsion work is "just for fun" for both of us. I'm afraid it's not that easy to do MSc thesis on emulsion making to the department of computer systems .
Click to expand...

'In the pioneer days, photographers had to make their own emulsions, and it was by the combined efforts of a small coterie of experimenters at the end of last century that the modern "dry plate" came into being. Some of these men were pure amateurs, others were practical chemists and men of scientific training. Out of this little band of experimenters came the founders of most of the original commercial emulsion-coating factories.' (T. Thorne Baker, Photographic Emulsion Technique, 1941, p.x).


I will be delighted to publish any and all of your 'just for fun' on TLF. Thank you very much for sharing your background. It sounds like you and your friend are in a great place for photographic exploration.
 
Awesome results! thank you so much for sharing them with us. You set quite an high benchmark for film quality.
 
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.

PE
 
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.
 
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
 
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.
 
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
 
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.


hrst said:
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.
Click to expand...
 
Thanks PE.

 
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 .
 
Last edited by a moderator:
Notes of this emulsion

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:



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: Dead Link Removed. 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!
 

Attachments

  • addition.gif
    1.4 KB · Views: 211
Last edited by a moderator:
You must log in or register to reply here.
Menu
Log in
Register