Making your own film

[rmazzullo]

Thanks, Ben...

I saw this also, but does this apply to glass plates only, or can this be applied to film base as well? The thinking here is that since a glass plate is not flexible, the emulsion may be less likely to chip or peel off when using that particular subbing formula. Since film base is very flexible, something different may be needed to insure the emulsion adheres completely to the substrate during coating, and doesn't chip off or peel away after it dries, when cutting the film down to size.

Thanks,

Bob M.

 

[ben-s]

I don't know.
In other places PE has suggested that the addition of sorbitol increases the flexibility of the emulsion.
Whether this would work on a subbing layer though... I would have thought it probably would.

 

[rmazzullo]

another idea....

I have another idea that I need to flesh out, but I wanted to share the basics regardless, with the group. I am thinking about mating a steel roller right ahead of a coating blade to flatten the substrate (film or paper) just before the emulsion is deposited. The supposition here is that the roller will smooth out any buckling or warping so the coating blade will not drag or get caught on the substrate itself, lessening defects.

This is presuming you are coating one sheet at a time, and is not meant (at this time) to describe any kind of method or system intended to coat a continuous roll of substrate on a micro level.

I have to work out the details, and have no idea if it would be practical, but it sounds possible. More details to come as I work them out.

Your comments / thoughts are appreciated.

Thanks,

Bob M.

 

[ben-s]

Bob;
Interesting idea, although from my (very limited) experience of coating, the paper usually buckles after coating. Curling and buckling are not problematic before you wet the paper.
On several occasions, I have had the emulsion end up in pools in the buckled paper.
For this reason, I have taken to coating on wet paper as follows:

Place paper to be coated in a bath of warm water.
Fill syringe from pot of melted emulsion.
Remove paper from water and squeegee down onto Contiboard (melamine faced chipboard) or plastic sheet.
Place blade in position and fill well with emulsion.
Coat.
Leave emulsion to gel off while returning blade and syringe to tempering bath.
Peel sheet from coating support plate, inspect and dry.

 

[AgX]

adherence to base

In literature two means of achieving adherence of the emulsion to a flexible base are given.

-) Using a sublayer out of gelatine but not using water as solvent but a solvent which was used as solvent for the base, or can act as such, as acetic acid (in case of cellulose ester).

-) De-estering the surface of the base, yielding cellulose molecules again.
This should be done by saponizing. (I got no idea how that would work.)

 

[AgX]

UV-film

Concerning that idea of Bob to gain an UV-sensitive film:
The problem of the absorbtion by the gelatine and the low sensitivity of using a halide only sensitive to the very low end of the spectrum could be tried to be overcome by doing it the other way: using a more complicated emulsion, panchromatic with added dyes which show fluorescence caused by UV-radiation. This would yield a boosting effect.

 

[AgX]

adherence to base (correction)

...but a solvent which was used as solvent for the base, or can act as such, as acetic acid (in case of cellulose ester).

Somewhere else those authors state (glacial) acetic acid as solvent for cellulose diacetate. For cellulose triacetate they state methylene chloride. But as they also state polystyrene as virtual insoluble in all organic solvents, their statements on solvents seem questionable to me.

 

[rmazzullo]

sources of subbing layer information

AgX,

Thanks for the information about the subbing layer components. Can you please be specific about the sources of information, and share with us where this material came from, and the authors?

I am sure there are proper handling procedures and precautions regarding glacial acetic acid. Out of the bottle, it will give you one hell of a burn. Not fun to experience unless you are trying to get rid of some warts.

Bob M.

 

[AgX]

"LP Clerc's Photography -- Theory and Practise"
4th ed. 1970, volume 3 "Films", chapter 21
authors: D.A. Spencer, L.A. Mannheim

(In the second amateur lab I worked in the owner had a bottle of glacial acetic acid stored. I'm not sure whether we made a stop bath of. Most probably we did.)

 

[ben-s]

I am sure there are proper handling procedures and precautions regarding glacial acetic acid. Out of the bottle, it will give you one hell of a burn. Not fun to experience unless you are trying to get rid of some warts.

And how! A colleague of mine used to work in a school as a lab tech.
One summer holiday, a small cylinder of gas fell from a shelf onto a crate of glacial acetic below, breaking several large bottles. Over the holiday, it oozed over most of the lab, and did rather significant damage to the floor and bottoms of cabinets and instruments standing on the floor.
It was apparently a hell of a job to clean up.

 

[rmazzullo]

more items needed....

I have scrapped the idea of putting a steel roller ahead of the coating blade, since Ben pointed out that there is no curling or buckling problem before you coat. PE had mentioned a while ago that what is needed is a heated vacuum table, to hold the substrate in place. I don't recall if he meant while coating or afterwards, but a vacuum table should do the trick either way.

I am kicking around ideas to do this, keeping in mind PE's warning that it isn't cheap. What I am concerned with now is how to alternately heat then cool the platen as needed, as well as creating just enough vacuum to hold paper or film, but not distort it. If the vacuum is too strong, it might create dimples in the support where emulsion will pool during coating. If the vacuum ports are kept below .005" in diameter, the film or paper support held by the vacuum should be too "thick" to distort.

Any ideas / comments are appreciated.

Bob M.

(I am still researching subbing layers and ways it can be done on a small scale).

P.S. we still need a way of measuring pAg reliably, and not expensively if we are going to try to tailor emulsions more closely, and with better repeatability.

 

[dwross]

Bob:

You might try mixing up a batch of emulsion and coating it. You're making this thing waaaaayyyy too hard.

http://dwrphotos.com/blog/Section7/Papers.htm

Denise

 

[rmazzullo]

Hi Denise,

I ordered supplies and equipment; I am just waiting for them to come in.

Bob M.

 

[dwross]

Congratulations Bob! Learning to make emulsion may be as much fun as a new puppy.

That's the first time I've thought of the comparison. It leaked out the brain and straight to the fingers. Actually, it's not bad. Concentrate on house training and bonding play first, and the obedience will follow along almost by itself.

You're going to have a blast. Keep us informed.
Denise

 

[rmazzullo]

cobalt chloride instead of rhodium chloride?

PE,

Can you please tell me if cobalt chloride was ever used to increase contrast much like rhodium chloride? Assuming it is in the same "family" as rhodium chloride (a heavy metal salt), could this be used as a lower cost alternative?

(I know you are busy with the emulsion making workshop this week. Whenever you get a chance).

Thanks,

Bob M.

 

[Photo Engineer]

I don't know of any formula that used Cobalt salts. That is not to say there are none, but no Kodak formula I knew of did, nor did any from other manufacturers that I have studied.

PE

 

[Photo Engineer]

Thinking this over more, I would suggest that the citations listed in our patents on cobalt incorporation into coatings would be a good place to start a literature search. Our work on cobalt incorporation involved a lot of work on prior art. Maybe this would help.

My co-workers and I probably did more work on cobalt in coatings than anyone else. IDK for sure but the patent searches were rather complete and the citations were definitive in this area IIRC.

PE

 

[rmazzullo]

Differences in gelatin

Hello PE,

I know there have been previous discussions about the differences between active and inert gelatin. Have there been any discussions about the Bloom rating of gelatin, and its effect on emulsion making?

How does the "Bloom" rating of gelatin change an emulsion formula? Are there other changes that should be taken into consideration (changes in viscosity), or -- properties that can be taken advantage of -- by using gelatins with different Bloom numbers?

Thank you,

Bob M.

 

[Photo Engineer]

Bob;

Bloom rating gives an indication of viscosity and ability to peptize (or surround) the silver halide crysta. It has nothing to do with the 'bloom' in German literature on photography related to ripening of emulsions.

We did not use it at EK as it is meaningless when doing coatings with a slide hopper, and it is also meaningless when doing ISO washes with PA gelatin. We used special gelatins for precipitation.

Usually we favored high BI gelatins of about 250 - 275.

PE