Hypersensitization

In the old days when TechPan was the standard film for astrophotographers every amateur astronomer knew what hypersensitization is, and many used it. It's a method to increase film speed and reduce Schwarzschild effect.

In a nutshell:

The films are treated in "forming gas", a mixture of 10% hydrogen and 90% nitrogen. Some people used 100% hydrogen (keep in mind that hydrogen is highly explosive) with recipes like this one:

"Put the film onto a reel and put the hole into a light and gas tight tank (in total darkness of course).
Create a vacuum to remove the oxygen out of the tank. Then fill the gas into the tank up to a pressure of 1.1 bar.
Heat the tank up to about 57 °C and back the film for about 8 hours 15 minutes.
After backing the film, remove the gas and wait until the tank cools down to normal room temperature.
Then remove the film out of the tank. Keep the hypered film in your refrigerator at -25 degrees centrigrade.
Hypered TP 2415 can be stored at -25 degrees centigrade for about 1 year without loosing its sensitivity.

My parameters for hypering Technical Pan 2415 are:

- 100 % hydrogen
- 1.1 bar pressure at 20 °C temperature
- 56 - 58 °C temperature
- 8 hours 15 minutes backing time"

This is not a typical home lab procedure, of course. I would not feel very comfortable if I had to heat up a tank that contains hydrogen, images of the Hindenburg Zeppelin come to my mind...

Just because I am curious and often use Infrared film at about 3-6 ASA, did anyone ever try this method with modern films?

I agree that this is too complicated to accomplish in a home lab, but your fears of something like a Hindenberg disaster are quite unfounded. The autoignition point of hydrogen is 1085 ºF (585 ºC). You're worried about 56 - 58ºC?

An outfit named Lumicon used to sell a series of "home hyper-sensitization outfits" back in mail order catalog days. They sold the gas, too. You could also buy hypered film, but it was expensive. Back in the day, though, if you were a serious astro-photographer, you hypered.

If I recall I saw something like this with Hydrogen Peroxide. I tried it once about 10 years ago and did not do the best job of it as the strong Hydrogen Peroxide ate my film due to contact with the solution. (yes, I would expect that to happen, I just didn't expect the stuff to touch the film.)

I think I found the formula in the darkroom or film cookbook.

I used hypered film exactly once, when I was studying astronomy in college. If I remember correctly, the film I used was a 400-speed Fuji slide film... the results weren't stellar (sorry, couldn't resist) and I never got more involved in the process. In lab we used CCD cameras, I was just playing around with the film. Here is a good article on the process. Lumicon are still around but it appears they no longer sell the equipment used for hypering. Hypered infrared film sounds interesting!

rthomas said:

Hypered infrared film sounds interesting!

Click to expand...

This could translate to "NO TRIPOD"

Several methods of hypersensitiztion have been described over the years. They have varying degrees of effectiveness with various films and processes. The effects are usually modest, maybe a stop. Most of the techniques are pretty obscure. Predictably, I could not find any in my reference collection, although I know I have them somewhere. Most of the hypersensitization processes I've seen involve exposure of the film to vapors shortly before use. The effect wears off pretty rapidly. Ammonia was one of the first agents used. Your adventures with hydrogen peroxide failed partly due to poor technique. As I recall, the method involves suspending the film about a inch above a pool of 20 percent hydrogen peroxide heated in a water bath to something like 40C. I don't recall the details. The technique I saw for using hydrogen to sensitize Technical Pan film was similar to what you described, but it used 5 percent hydrogen in dry nitrogen. This is supposed to work better than pure hydrogen. By the way, hypersensitization of Technical Pan only worked for high contrast applications, such as astrophotography. Another, non-chemical method is exposure to weak light. The technique is somewhat like flashing, but the light levels are lower. Green light, usually from a No. 3 safelight, was generally used. I'm not sure how well any of these techniques would work with modern film. I'm also not sure what effects these processes would have on fog level, contrast, grain, or subsequent processing.