Film emulsions

[Photo Engineer]

I have now repeated the film emulsion on paper and film support at 3 workshops and about 6 times alone. All the results indicate that the film speed is about 25 to 50 and the paper speed is about 100 - 200 with significantly higher fog.

The higher speed and fog on paper is normal due to back reflection and the relative coated silver levels.

Now, here are the problems as I see them:

1. Contrast and Dmax vary and are much too low. There is too much unused silver and I have to fix that.

2. There is too much variation in contrast, dmax and fog from coating to coating and batch to batch.

3. Under magnification there is a slight appearance of specks. These are not pepper grain, as they are colorless and are not present in fixed out stock. I believe it is just darkroom grunge and I need to use a finer filter for the emulsion before coating and just patiently wait for the thick emulsion to run through the filter.

4. This is an SRAD (Single Run Ammonia Digest) emulsion and the smell of ammonia during digestion is so strong even in a large darkroom that it is hard to make large batches. The small batch size may be contributing to the overall variability.

5. The chemical sensitization and the digestion take too long to get the speed I want.

6. I am starting to run out of transparent subbed support, and may have to find another source for continuing these experiments. My thanks to Jim Browning for the supply that I do have.

Therefore, I am going to revisit this emulsion and try for a better design that uses another solvent than ammonia for digestion and a better workup method than the one presently used. My speed aim will remain in the ISO 50 speed range and the sensitivity aim will remain orthochromatic. The results to date do not seem to suffer from a lack of sharpness or any problems associated with having no AH layer, but I do have the dye for addressing this problem.

I may have to continue this work making paper negatives for a while to conserve film support and only make film coatings when I know things have been 'fixed'.

PE

 

[Photo Engineer]

For those interested, here is the latest ISO 40 effort. It is ortho sensitive.

This is a scan of a portion of a 4x5 negative that is about 2x3 in size. The scanning process improved image quality, but there were no intentional changes made to the image.

It is grainy, but surprisingly sharp. There are a number of defects due to scratching of the soft emulsion, and some signs of what might be a bit of reticulation. It was processed as soon as it was dry after being coated, so it was pretty 'fresh'. The ISO 20 test negative was considerably lighter and lower in contrast by virtue of being on the real toe, so this is an affirmation of the speed of the emulsion being close to 40.

I hope this looks ok after uploading. BTW, there was no residual color from the erythrosine sensitizing dye which was used to get ortho sensitivity.

PE

 

[Photo Engineer]

For those interested, here is the wedge spectrogram of the ortho film. The sensitizing dye was erythrosine.

It was an example on paper from a different run of the emulsion.

I'm sorry to say, the only film sample from this run with a wedge spectrogram was from a defective piece of film, and the only paper sample from this run was ruined because the shutter on the spectrosensitometer hung up.

The image was done with no UV absorber, so you see the full UV sensitivty on the left of the image out beyond 400 nm and on the right, you see some indication of red sensitivity, but this is actually an artifact of having no UV absorber. It is a harmonic of the UV.

Ah well, nothing is perfect.

PE

 

[r-s]

Very impressive image. Good "evenness" of the image compared to some other efforts I've seen.

I have not tried making any emulsion (yet), but I've had some ideas bouncing around in my head, that I thought I'd bounce off you to see what you thought of them.

Two main themes at the moment. First is a (maybe) novel method for forming emulsion, which would allow daylight coating (if it works). Basically, I would mix colloidal silver into gelatine, and then coat the support (glass or flexible) with the gelatine/colloidal silver emulsion. (At this point, the emulsion would be black, entirely DMax across the surface.)

Then, I'd go "lights out" (or, put it in a tank), and soak it in a halogenating bleach (i.e., potassium bromide and potassium ferricyanide, to make a silver bromide emulsion), and then, rinse, and dry.

In theory (my theory, at least), I'd then have a silver bromide emulsion (non-color sensitized).

You think this'd work?

Next theme is coating methods. From what I've read, the "blade" technique causes people a lot of grief, trying to get a nice, even coating. It seems to me that this technique will work nicely if everything is done just right, but, it is inherently lacking in any "self-regulating" characteristics,

So, what I am thinking is that two "possibles" would be to either spray the emulsion onto the support, or, use some type of laminar flow system to "run" it over the support.

A third possibility, which I think I recall having read that G. Eastman patented as his first "simple" method for coating plates, would be to use what I'd call a sort of "offset" system: A roller (rather large) sitting in a tray of liquid emulsion, which rotates, picking up a coating of emulsion, which is then transferred to a sheet of glass that passes horizontally along the top of the roller. (The roller would be "wet" with emulsion just prior to contacting the plate, and then "dry" (emulsion layer completely transferred) on the side that had passed the plate.)

I think this system would have a good measure of "self-regulation" of the coating process, but, be more trouble than it's worth for a very small hobby enterprise.

 

[Hologram]

Two main themes at the moment. First is a (maybe) novel method for forming emulsion, which would allow daylight coating (if it works). Basically, I would mix colloidal silver into gelatine, and then coat the support (glass or flexible) with the gelatine/colloidal silver emulsion. (At this point, the emulsion would be black, entirely DMax across the surface.)

Then, I'd go "lights out" (or, put it in a tank), and soak it in a halogenating bleach (i.e., potassium bromide and potassium ferricyanide, to make a silver bromide emulsion), and then, rinse, and dry.

In theory (my theory, at least), I'd then have a silver bromide emulsion (non-color sensitized).

You think this'd work?


Actually, it has been done to make Lippmann emulsions. There's a 1929 French paper (http://www.holographyforum.org/lipp...metrie_de_plaques_photographiques_a_grain.pdf) describing such a method (by the way, there are a great many papers dealing with the making of Lippmann emulsions available at:
http://www.holographyforum.org/HoloWiki/index.php/Lippmann_Papers).
Ferricyanide doesn't seem to be a good solution for the bleach though. Leroy used a diluted copper sulfate bleach. Ultimately, the emulsion was spectrally sensitized.


A third possibility, which I think I recall having read that G. Eastman patented as his first "simple" method for coating plates, would be to use what I'd call a sort of "offset" system: A roller (rather large) sitting in a tray of liquid emulsion, which rotates, picking up a coating of emulsion, which is then transferred to a sheet of glass that passes horizontally along the top of the roller. (The roller would be "wet" with emulsion just prior to contacting the plate, and then "dry" (emulsion layer completely transferred) on the side that had passed the plate.)

Mayer bars might be another option...

H

 

[rongui]

6. I am starting to run out of transparent subbed support, and may have to find another source for continuing these experiments. My thanks to Jim Browning for the supply that I do have.

PE

I have been making emulsions for a short time and I have found that "Grafix Dura-lar Wet Media Film" coats very well.

It is available in the US in Hobby Lobby Stores or online at Dick Blick http://www.dickblick.com/zz555/07/


Ron

 

[Photo Engineer]

Ronqui;

Thanks. I'll have to look it up.

PE

 

[Photo Engineer]

r-s;

Yes, as stated above, your method will work but the emulsion will be very slow as no method is provided to control grain size or apply chemical (sulfur) sensitization. Spectral sensitization could work, but would require massive amounts of dye due to the grain size, as this is a surface effect. See the other thread on this regarding dying coatings by imbibition.

Spray coating is covered in the book "Silver Gelatin" and is a way to achieve film and paper coatings. Using a paintbrush works. The offset roller method works and was used in production. The blade works also and was once used in production as well as being the method used for hand coating. One thing common to all of these is what you point out, in an indirect manner. It is an art and takes a lot of practice. The fortunate thing is that you can do it with dyed gelatin which is a lot less expensive than silver.

Denise Ross has been able to achieve exellent coating quality within just a few weeks effort, as you can see from her posts.

Hope that helps.

PE

 

[r-s]

I wonder if melted emulsion would have viscosity conducive to a laminar flow setup? It wouldn't take much by way of equipment -- wouldn't even need a recirculating pump for a minimal system, i.e., place paper in angled holder, fill upper trough with melted emulsion, open the floodgate, and then collect the excess at a "catch-trough" at the bottom (and then remove the coated sheet).

 

[r-s]

With respect to dyes, couldn't they be coated on the metallic (colloidal) silver prior to embedding it in the emulsion?

 

[Photo Engineer]

Melted gelatin has good laminar flow. That is how current 'slide' coatings are made in production. Viscoscity can be customized by changing concentration or temperature.

Sensitzing dyes cannot be added to metallic or colloidal silver. This is similar to trying to sensitize a Daugerrotype. Many have tried, and all have failed.

PE

 

[r-s]

Melted gelatin has good laminar flow. That is how current 'slide' coatings are made in production. Viscoscity can be customized by changing concentration or temperature.

Well now that gives me some hope! I may spend some quality time with some ABS plastic and pipe cement, and see what I can whip up! (The state of my health is such that I do not forsee a happy outcome to any technique requiring the sort of manual dexterity requisiste in the blade system. Also, the former software engineer in me makes me tend to try to work up self-regulating systems that take care of the "fine tuning" on their own.)

Sensitzing dyes cannot be added to metallic or colloidal silver. This is similar to trying to sensitize a Daugerrotype. Many have tried, and all have failed.

Well, look at how many times it took Edison before he came up with a viable incandescent filament. (And just to be fair and balanced look at how his rival Tesla was unable to persuade anyone of the viability of AC power transmission systems.)

I'm wondering if perhaps during the creation of the CS, the electric charge in the water might be able to be used to perform something akin to anodization of the dyes (bonding them onto/into the grains as they form)? I know that the size of the silver granules can be regulated via voltage, current, and time duration (the longer you run the process, the more the conductivity of the medium goes up, and the larger the grains become). I believe it's possible to create some fairly large grains, if desired. (Generally the goal is to create the smallest sized grains as possible, with larger grains being an indication of the process having gone awry, but most of the people using that process are not using it for photographic purposes.)

 

[Photo Engineer]

The binding of a sensitzing dye to the surface of a silver filament or deposit of any sort would be disrupted by oxidation and the dye would be removed, and then the silver halide would form in the presence of a very low concentration of dye, if I understand your process properly.

It would be more useful to form the silver halide and then dye it, even in situ although the speed would be low.

Remember too, that Edison was not a very nice person, but persistant. It took him years to develop his electric light. And, Tesla was also in favor of using the natural energy of the earth. He claimed to cause earthquakes by vibrating metal bars at the natural frequency of the earth and he said he could broadcast energy waves all over the earth to power equipment or to be used as weapons. Some things work and some don't. Give it a try and see what happens.

PE

 

[Bromo33333]

R[... Tesla] said he could broadcast energy waves all over the earth to power equipment [...]

That actually would work - except the system would be rather inefficient, and in some places the RF voltage would be so high you would draw arcs randomly.

He was a brilliant man, who had NO people skills, and became the architypical "mad scientist" - later in his life he would have a birthday press conference and say things like "...They said it wouldn't work... but I'll show them! My death ray will transform the world!!!" all wild eyed.

Transformed our world (Radio, Radio control, AC power, etc.) but died penniless and alone. Sad. If only he had become a photographer!

 

[Photo Engineer]

That actually would work - except the system would be rather inefficient, and in some places the RF voltage would be so high you would draw arcs randomly.

He was a brilliant man, who had NO people skills, and became the architypical "mad scientist" - later in his life he would have a birthday press conference and say things like "...They said it wouldn't work... but I'll show them! My death ray will transform the world!!!" all wild eyed.

Transformed our world (Radio, Radio control, AC power, etc.) but died penniless and alone. Sad. If only he had become a photographer!

Yes, very sad. His patented earthquake machine was never made to work by anyone but him, but he said that it brought down a building and caused an earthquake in Denver(?). They recently tried to duplicate some of this work on Mythbusters on the DISC channel.

They drew some rather nasty cartoons of him in his later life.

PE

 

[robopro]

Developing 'home made' gelatin emulsions

Not to change the subject back to the original thread, but would I be correct in assuming the gelatin emulsion made by Phto Engineer would be developed using a normal B&W process, like D-76 -- or would you use a stronger developer like Dektol?
Also, have you ever tried doing direct silver positive development to produce an ambrotype effect? If so, how did you do it?

 

[Photo Engineer]

I have used Dektol 1:3, 1:2 and 1:1 right now, but that is not to say that D76 could not be used. I just keep Dektol around for standard testing and use that by habit.

I have used other developers to good effect, but right now Dektol 1:3 for 3' looks like a good film develper to me.

There is no reason that a silver positive could not be made with appropriate processing. I would use D19 or D8 or D11 (a high contrast developer) for the first developer and then a non-rehal bleach, a clear and redevelopment in the light, just as in a conventional process.

I have no intention of producing a direct reversal emulsion however. This is an emulsion that gives a reversal image directly from a single development step.

PE

 

[robopro]

'1 have no intention of producing a direct reversal emulsion however. This is an emulsion that gives a reversal image directly from a single development step.'


Why not? You could bottle it and make a fortune -- like Rockland Colloid did with Liquid Light!

And just to show my ignorance (as if you couldn't see it already), how does a direct reversal emulsion work?

 

[Photo Engineer]

There are several types of reversal emulsion that rely on different mechanisms. This was one area that I didn't get into much as they were pretty much history by the time I enetered emulsion work. They were used in the Kodak instant film primarily.

The most prominent relied on a core shell emulsion which trapped the negative image internally and used a nucleating agent to 'fog' the surface to yield a positive image. The nucleating agent was (IIRC) a hydrazine derivative called a hydrazide. Since I did my thesis on hydrazides and hydrazones as well as azo chemistry, I followed it pretty well, but have forgotten most of it.

I have some notes here somewhere if you are really interested, but I have not looked at them for years. If you are interested, I could look them up, but I can't promise how complete they might be. Sorry.

In any event, I have enough on my plate right now without getting into these rather more complex emulsions. I want to make 3 emulsion types and do them well and do them simply.

1. Contact emulsions in 3 grades. Pretty much done. They are equal to or better than AZO.

2. Enlarging emulsions in 3 grades. I have 2 out of 3, working on the next one. These are a cross between Brovira and Kodabromide.

3. Negative film emulsion with ortho sensitivity and about 25 - 100 speed. I'm getting 40 speed regularly with high fog and low contrast. I'm working on this.

4. Move on to color??????

Enough for me do you think?

PE

 

[roteague]

Time to clone you Ron.

 

[Photo Engineer]

Bob, I think my clone and I would be 'dead ringers'. Hmmm, what I really need is an apprentice who is here in Rochester and interested in this kind of thing. Anyone out there listening????

PE

 

[MattKing]

Time to clone you Ron.

No, just "duplicate" him

Matt

 

[ben-s]

Bob, I think my clone and I would be 'dead ringers'. Hmmm, what I really need is an apprentice who is here in Rochester and interested in this kind of thing. Anyone out there listening????

PE

I'd love to, but I live and work in the UK!
Could you invent a teleportation device?