effect of pressure on emulsion sensitivity

[Hypoxic]

I've been reading and cross referencing as much as I can trying to compare the emulsions and how the mixing and ripening affect their speed and then I came across patent: "Superatmospheric pressure used to improve the sensitivity of silver halide emulsions" US3542557

The patent claims subjecting a silver halide emulsion to 3000psi-6000psi for 16+ hours increases the speed dramatically and they provide data demonstrating a 100 speed emulsion subjected to 2000psi nitrogen atmosphere for 24 hrs yields a change in structure delivering a 400 speed emulsion.

I've searched and searched on APUG and I can't find mention or reference to such a process... is this a valid technique or anybody familiar with this.

 

[Gerald C Koch]

I would hazard a guess that the technical requirements (2000 psi, ...) are beyond what APUGers are capable of duplicating.

 

[keenmaster486]

Just blow on it really hard. That'll work fine.

 

[pdeeh]

I would hazard a guess that the technical requirements (2000 psi, ...) are beyond what APUGers are capable of duplicating.

The patent makes claims for not less than 30psi, not less than 50psi, and "about" 2000psi as separate cases where improvements are found.

So in some parts not impossible for an APUGger with access to industrial equipment as part of their job or at a University, for instance.

 

[AgX]

The patent claims subjecting a silver halide emulsion to 3000psi-6000psi for 16+ hours increases the speed dramatically and they provide data demonstrating a 100 speed emulsion subjected to 2000psi nitrogen atmosphere for 24 hrs yields a change in structure delivering a 400 speed emulsion.

But they also were yielding a quadrupling of gamma!

 

[Wallendo]

The patent makes claims for not less than 30psi, not less than 50psi, and "about" 2000psi as separate cases where improvements are found.

So in some parts not impossible for an APUGger with access to industrial equipment as part of their job or at a University, for instance.

30 psi is just 67.5 feet of seawater, 50 psi is 112 fsw. It would be easy to go on a deep sea fishing trip and compress some liquid emulsion this way. Put it in an airtight wine bag and drop it overboard at night with a weight for a while. You'd need some really deep water and a long rope (4500 ft) to get to 2000psi however.

 

[pdeeh]

Hehe temperature control might be a challenge with that method

 

[Hypoxic]

Wow.. more response than I thought. The patent is old and I'm hoping somebody here has experience as surely the majors have tried but could not scale it.

I'm an eCCR guy and and pump 5000psi lab clean "zero" air through hyper-filter stacks/sieves in my garage..the pressure and temp is a non issue for me. All scuba, paintball, scba are available >=3000, and welding gasses usually come in at 2200psi+ depending on gas so a small vessel, gas whip, CGA fittings, and a few swagelok parts is not out our range for the APUG community.

I was thinking surely crystals grow best under pressure as they do in caves/deep and with a little searching I came across the patent which verified my assumption. I'm getting ahead of myself as I need to make TLF1 first before I go nuts with this, but this avenue seems promising.

 

[TattyJJ]

Nitrogen comes in bottles at between 2000 and 2600psi and is cheap and easy to get hold of. I though most inert welding gasses are closer to 1000...?
The hard part might be finding a regulator/fittings that will deliver full bottle pressure.

In my line of work it would be pretty easy to manufacture the fittings and a small steel box that the film could be placed in and could handle the pressure.

But i'd want a pretty sturdy wall between it and me, no matter how sure you were it could take it, at those pressures if it let go would be like a small bomb.

But none the less an interesting idea. Kinda like hypersensiting film without the very difficult to get (in the UK at least) forming gas.

 

[Nodda Duma]

I find myself wondering how that actually increases sensitivity. I would expect this to occur due increase the concentration of silver halide grains per unit thickness of emulsion when the emulsion is compressed. As such it would have a similar effect as if you were to increase the concentration of silver halide when mixing the emulsion and coating under normal pressures.

Is that a sound theory?

 

[AgX]

No, as the emulsion is coated and exposed under atmospheric pressure.

And furthermore sensitivity is only dependent to a certain degree on crystal concentration.

 

[Photo Engineer]

Is that a sound theory?

No.

 

[Photo Engineer]

I would have to say that if this were feasible, then it would have been used. I think there were problems reducing it to a real usable process in manufacturing and it was abandoned. I knew one of the inventors and he never mentioned it at all during our work together.

PE

 

[Gerald C Koch]

Astronomers routinely hypersensitize plates with nitrogen under pressure. However the effect only temporary and the plate must be used within a very short space of time. In fact the various hypersensitization and latensification methods have a limited effect.

 

[Photo Engineer]

Try here: https://en.wikipedia.org/wiki/Photographic_hypersensitization

You can also use Hydrogen.

This particular effect does not need high pressures AFAIK and works only at very very long exposures such as used in astrophotography.

PE

 

[Fraunhofer]

In astro photography hypersensitization with hydrogen gas (probably mixed with some other stuff) was used not so much to increase speed but to delay onset of reprocity failure. Taking exposure time from 2 days down to 2 hours

Problem was film treated that way had a very limited shelf life. DIY is tricky because if you're not careful you have a hydrogen bomb (of the chemical variety, still...)

 

[Photo Engineer]

Yes, as I referred to in my post about long exposures.

PE