Hyper-Sensitizing Slow Emulsions

[Drew Bedo]

In the hay day of 35mm film, the Astronomy magazines used to have ads for gear and materials that hyper-sensitized films for astrophotography. Years ago, I ran across a reference to this technique being used with the glass plates used for serious scientific work at an observatory.

Typically, these treatments involved soaking the emulsion in an oxygen free gas (don't remember what gas) at some moderate pressure and a temperature somewhat above room temp.

Do any of these techniques have a place in glass plate photography today . . .Wet or Dry?

[Nodda Duma]

Hypering gas was an 8% hydrogen / 92% nitrogen mix. I used to do this for astrophotography using Tech Pan.

Here is a page on Jerry Lodriguss’ website discussing the details of hypering film. The discussion would apply to dry plate as well.

http://www.astropix.com/html/astrophotography/film/hypering.html

[Mike in NY]

The use of forming gasses such as heated hydrogen, nitrogen, or a combination of the two, were effective at not only increasing the speed of plates, but dealing with reciprocity failure since the exposure times were greatly reduced. I know that forming gasses were effective at removing residual oxygen and H20 from gelatin emulsions, so I suspect it could do the same with today’s modern dry plates.

As for wet plates, I have a difficult time imagining a practical application (loss of light sensitivity as the wet plate dries over 10 – 15 minutes). Also, I suspect that the science wouldn’t be the same since the physical and chemical properties of a salted collodion plate are different from a gelatin plate.

[Drew Bedo]

Nooda and Mike:

Thanks for your input. Could be something I do in the future, but not immediately. The linked discussion focuses mainly on 35mm film. Experimenting or testing in LF could be steeply expensive. Besides all the other gear, a dry plate shooter would have to figure out how to create a pressure vessel for LF. It was done of course att observatories on pretty large plates.

And the question now is: Does anyone working in LF do anything like this now? Any increase over ISO 2 would be a help.

[urnem57]

This is way above my pay grade, but fascinating nonetheless. I am always amazed at how deep the impact of the photographic process is. There are so many specialties and disciplines that one can pursue using the tools of photography.

[dwross]

Nooda and Mike:

Thanks for your input. Could be something I do in the future, but not immediately. The linked discussion focuses mainly on 35mm film. Experimenting or testing in LF could be steeply expensive. Besides all the other gear, a dry plate shooter would have to figure out how to create a pressure vessel for LF. It was done of course att observatories on pretty large plates.

And the question now is: Does anyone working in LF do anything like this now? Any increase over ISO 2 would be a help.

The easiest way to get over ISO 2 would be to make a faster emulsion (at least with dry plate).

[jnantz]

The easiest way to get over ISO 2 would be to make a faster emulsion (at least with dry plate).
Hi Denise:
what's the fun in that :)
John

[konakoa]

Drew, I currently use this exact technique for 4x5 Tech Pan that I take out to my camera to get wide field views of the night sky. A few points to consider--to hypersensitize the film (Tech Pan at least) the process takes several days in a sealed light-tight and air-tight chamber. If you're doing wet plate I would imagine the emulsion would dry out long before the gas can do its thing. For dry plates, it could work. You'd have to do some testing. And one more consideration; the hypered film doesn't keep its enhanced sensitivity for long. About a week and a half is my experience. After that, the gains are lost and the film reverts to its normal sensitivity abit with a tiny bit of added base fog. So once hypered you need to use the film immediately.

[dwross]

Hi Denise:
what's the fun in that :)
John

�� Fun is the best reason of all to do what we do (whatever the heck it is we do!).