Making your own film

[rmazzullo]

Thank you PE,

I hadn't thought about blending the emulsions together. Would any kind of clustering or uneven distribution of the different size grains occur in a blending of emulsions as opposed to coating one layer above the other? Also, would the blend have to be "homogenized" just prior to coating, or could the emulsion blend be prepared prior to making the coating formula?

Again, thank you for these very helpful replies....

Bob M.

 

[Photo Engineer]

Bob;

I'm happy to try to help you or anyone.

If the emulsions vary greatly in composition or in addenda needs (such as antifoggant level being critical) then blending may be a problem, especially as the melted mixed emulsion holds before coating.

If that happens, then the blended emulsions gradually exchange chemistry or salts and start to change.

PE

 

[rmazzullo]

PE,

Thank you for the caveat regarding this idea. Another detail to add to the nomograph chart (and my notebook).

Bob

 

[rmazzullo]

chloride emulsion sensitivity

PE,

Can you please tell me, if chloride emulsions are UV sensitive, could a film based on this property be used as a "UV film" and shot with a quartz lens to pick up either reflected or incident UV? (adding other components that would be needed to make it a coatable emulsion are assumed).

Do you know if film products existed at one time that took advantage of this?

Thanks,

Bob

 

[Photo Engineer]

All emulsions are UV sensitive. Many glasses are UV filters removing a lot of the UV light present.

Chloride emulsions are mainly UV sensitive and tend to be very slow. All known methods of speeding them up, reduce UV sensitivity and increase sensitivity to visible light. Therefore, the methods in current use are self defeating of that purpose.

If you make a fast Bromide or fast Bromo Iodide emulsion you will probabaly get more UV speed than current pure Chlorides can achieve. That is an educated guesstimate, never having compared the two in a side-by-side experiment.

PE

 

[AgX]

Bob,
I guess you were referring to silver chloride as it yields the most extended sensitivity within UV and the least within blue. But what would you gain aside from making an UV filter (in the actual sense) obsolete?
You could use a rather common film with a rather thin coating (to reduce scatter).
I guess, again, that a microfilm would induce even more scatter than a pictographical film.

 

[rmazzullo]

how do dyes work?

PE,

When dyes are used for spectral sensitization, for example, can you please explain how the dyes change the sensitivity of an emulsion that was originally sensitive to other wavelengths (UV, etc)? Is this more a function of physics than chemistry?

Thanks,

Bob M.

 

[AgX]

This has become a four eyes talk I assume.

 

[rmazzullo]

This has become a four eyes talk I assume.

Agx,

What exactly does that mean? Was that meant as a derogatory statement?

Bob M.

 

[AgX]

Bob,

I found your idea of that special UV-film interesting (I like weird films etc.). But I really did not see the advantage, that was why I replied. I wanted to know what led you to that idea, perhaps I overlooked something. (Fast PE slipped inbetween.)

 

[rmazzullo]

Bob,

I found your idea of that special UV-film interesting (I like weird films etc.). But I really did not see the advantage, that was why I replied. I wanted to know what led you to that idea, perhaps I overlooked something. (Fast PE slipped inbetween.)

AgX,

Truth be told, I completely forgot about using a UV specific filter after the fact. I was thinking about the sensitivity of the emulsion itself, and if it could be used as a UV sensitive film, much the way infrared film is used. IIRC, you would also need a special lens that passes UV (quartz, I believe, but I could be wrong), because glass attenuates UV, as PE had mentioned earlier.

Come to think of it, you might be able to get decent results with regular film, a UV filter, and a quartz lens, but that is only a guess. I haven't tried it yet to see if it works or not. Plus, I would have to find a place to rent or borrow a suitable lens, as I heard they are expensive to buy.

Bob M.

 

[AgX]

You are totally right. But before looking for some quartz lens I would give a pinhole a try.

But you are waiting for PE to reply on that dye issue. I'm curious about his answer. (Look into your Mees&James it's quite a chapter, two actually, but concerning quantumphysics, or whatever that be, most probably not up to date.)

 

[Photo Engineer]

Guys;

Nikon makes a UV lens if you have the $$$ and your Yen is big enough (pun alert).

Sensitizing dyes adsorb chemically to the grain and pump energy of the specific 'color' of photon into the emulsion. They work in a manner similar to the Rhodopsins and etc.. in the eye.

Read Mees and James. Yes. There is quite an extensive section on them in there, much coming from the work of Paul Gilman and others who worked on sensitizing dyes.

PE

 

[ben-s]

I seem to recall reading somewhere about a Nikon UV lens.
"UV-nikkor 105mm" seems to ring a bell
I think I have a link at home. I'll try and find it later.

Edit - PE beat me to it!
I'll still try and find the link though

 

[AgX]

In the Mees&James (1968) it is indicated that it might be that the dye does not need to be adsorbed to the halide, as one would not be able to distinguish the effect of the adsorbed and just adjacent dye. I found that interesting. But I guess the book by T. Tani could serve better on this subject.

In the former there is a reference to colloidal silver which serves as a sensitizer with the halide being precipitated on it/with it.
Was that form of sensitation ever of any importance? Or was that rather a useful artefact while precipitating the halide?

 

[Photo Engineer]

There are all manner of methods of 'activating' spectral sensitivity including the adjacent molecule effect. One form of this is the "J" sensitization described by Dr. Jelley at EK. This is where one dye stacks on another and turns a green sensitizer into a red sensitizer. (That method, BTW, is used in Kodachrome film for the red layer.)

Dyes can also be made into salts with silver ion and form a sensitized crystal.

Many methods remain unpublished as well.

PE

 

[rmazzullo]

gelatin shrinkage

PE,

Thank you for the pointer towards Mees and James. Was the initial research into dyes based on the action of Rhodopsin in the eye? (Ok...big stretch there).

Can you please discuss how much an emulsion coat generally shrinks when it dries? Is the amount of shrinkage affected by the added materials used to prepare an emulsion for coating, such as a hardener, and / or the surfactant?

Thanks again,

Bob M.

 

[Photo Engineer]

I read the history of spectral sensitivity years ago and have not really looked into it in Mees and James. I can say that chlorophyll was once used as a sensitizer. It has a varied history to say the least.

A coating 'melt' shrinks dependant on what it contains. I have seen 0.005" of wet melt shrink to 100 microns or 10 microns depending (sorry for the mixed measurements, but we used one for coating and one for cross sections and that is the way I remember it).

PE

 

[rmazzullo]

more gelatin....

PE,

Thank you for the reply. I have more questions about dyes, but that will have to wait until I read the chapters in the Mees book.

To continue a little further with the gelatin question; this implies that in multiple layer films (color film) each emulsion layer would have been designed to dry to a certain thickness as part of the entire stack. In films you were are familiar with, can you disclose how thick some of those individual layers were when they were dried (if it's not going into the proprietary zone)?

And, how were they able to determine that 'x' wet thickness of gelatin would dry down to 'y' thickness? It would seem then that you would have to figure out how much silver you would need to have in the emulsion per square foot for a given thickness dry, depending on what result you wanted the emulsion to produce. I think. I could be really off track here.

Thanks again,

Bob M

 

[Richard Mendales]

Nikon made a 105mm F4.5 UV Micro Nikkor in the 1980s, using fluorite and quartz glass. It was able to bring visible light and UV to a common focus, so that you could use it without having to correct focus as you normally have to do for infrared. I always wanted one, but haven't seen any on the used market since I could afford it.
Regards, Richard

 

[Photo Engineer]

There are methods to calculate the dry thickness of a wet layer from the solid content.

Each layer in a multilayer color film is designed to dry down to a preselected thickness based on this calculation.

PE

 

[AgX]

the invisible...

With reference of that idea of an unsensitized UV-film of rmazzullo, there once was an idea of a special color film:

“As an extension of this, the layers may not be colour sensitized at all, but show up differential penetration of electron beams or X-rays so that the colour result represents the relationship of different kind of invisible radiation.”
D.A. Spencer “Colour Photography in Practice” 5th ed. 1966 p.64

To my knowledge no such film has ever been marketed, and, a guess, would be obsolete to the science world now. But could be used as a digital-to-analogue printfilm. I’m doubtful about the differentiation between the energy levels. Though as one would only have to use three energy peaks, as typical for print films, that would be easier to achieve than yielding a spectrum.

 

[rmazzullo]

some early patents on emulsion making

Hello all,

Here are a few older patents that describe making some simpler emulsions. Please take note of the theory behind the invention in these patents, as they detail important general emulsion making principles. One patent (3031304) describes making a fine grain emulsion, which I believe is another way of saying "Lippman emulsion".

This list was deliberately kept short. When you search using these as starting points you will find other, more intensely detailed patents. Some have amazing fabrication details of emulsions that are used as functional examples to support the described subject of the invention. At the very least, they do give a close look at techniques that are used to make more modern emulsions.

Patent numbers to look at: 3031304, 3320069, 2222264, 2592250, 2369449.

Search tip: go in reverse. (You didn't expect me to do all of your homework, did you?)

Thanks,

Bob M.

 

[rmazzullo]

reliable method of subbing polyester / acetate needed

Hello all,

Something else I have been researching, and need to nail down, is a good method of adding a subbing layer to a film base (polyester or acetate) that will allow coating of an emulsion. Some of the patents I have looked at so far have involved proceedures using organic chemicals that are either custom made and / or difficult to get. To properly sub a film base may include some type of surface treatment immediately prior to coating with the subbing layer, to prepare the material for later coating with emulsion (still looking at that).

Any ideas / directions would be appreciated.

Thanks,

Bob M,

 

[ben-s]

Bob;
PE posted this the other day:

10% gelatin 100 grams
4 ml 5% chrome alum stock solution (stock is 10% chrome alum)
5 ml Everclear (95% ethyl alcohol)
1 drop 10% thymol in iso-propyl alcohol.

This should give a good subbing layer for you coated using normal plate methods.

If it is too thick, just dilute with distilled water in steps until the desired viscosity is reached.

Here:
(there was a url link here which no longer exists)

I assume it would be coated as a normal emulsion would.