What is Gas Hypering?
This is the technique where film - 35mm, 120 roll, 4x5 plate film - is placed in a vacumn chamber. All air is removed. A mixture of hydrogen and nitrogen (usually 8%/92%) is introduced. The tanks is then heated for a period of time. During the heating, water and oxygen molecules in the emulsion of the film leaches out,a nd to some degree it replaced by the hydrogen. The removal of the water & oxygen heps inprove the reciprocity failure of film, whereas the hydrogen helps increase the film speed. The main drawback to hypering is that once treated, film should be used up and developed as soon as possible.
Some films such as Kodak's Tech Pan, especially if kept cool and dry, will last for weeks. However, I still find the best results come form using the film up directly and quickly as possible.
Hypering Film in Canada
I estimate only a dozen active amature astronomers in all of Canada who are hypering film. There are many, many more who have done so in the past, but a large number of them have gone on to CCD cameras.
Part of the problem is envriomental laws make importing hypered gas from Lumicon in California, USA, very difficult. Another problem is that in Canada any pressurized gas that contains even a hint of hydrogen must have a special hydrogen approved regualtor. There are not cheap - with taxes, a regulator alone will cost $300.oo CDN. As a result, I had to locally order the forming gas & tank.
The tank is another story. Lumicon sells hypering gas in 35 litre tanks. My tank is 2800 litres in size. When I asked my supplier if I could order a smaller tank, I was told yes...but - it was a 1000 litre tank, and being an odd size, ti would be a special order and take longer to be delivered. The worst part was - it would only be $5.oo less.
Is Hypering Worth the Effort?
Maybe. Depends on your situation, and what type of pictures you wish to take. See my little article on CCD vs Film to first help you decide which technology you wish to embrace. If you have decided conventional photography is the way for you to go, then here's my advice.
If you own or have access to a darkroom, and enjoy darkroom work, then it is not a big step into hypering. If you do not, then consider buying a few rolls of ilm or having another amature who hypers film do a roll or two for you to try first. There are some amatures who never hyper thier own film. While there are not many amatures in Canada hypering film, those who do are spread evenly accross the country. Contact you local RASC Centre or astronomy club to find these people. My links will lead you to the locations & addresses of these place.
Factors that affect Hypering
There are many, many factors that will afffect how a film hypers initially. Some of these are....
- variations in the film emulsion every time a new batch is made up;
- variations due to use of hand pump vs mechanical pump;
- differences in the quality and strength of your forming gas;
After the film has been hypered, many factors will affect how it actually performs in use. Humidy is a real killer of hypered film. Some astro-photographers had modified their cameras/film holders such that they can be purged with nitrogen or a constant flow of nitrogen left to run over the film. Emulsion on all films has a "memory" for the lost water, so do all possbile to keep film dry. If planning to go out on a humid night, consider using non-hypered film.
Cold weather is a positive bonus. Canadian winters act like a natural cold camera. My comet picture on the main page is an example of tech pan shot during a cold night (-10C) where the film was only hypered to 25% of the "normal time".
Processing a film can affect your outcome too. Photo chemicals are compatable across brand names, but at least in B&W, each brand of developer will affect your negative, even the ratio of the dilution. Local hardness of water can affect your processing. For this reason I perfer home processing, as it gives me more control over all the variations.
What ever technique you use, the most import thing to do is BE CONSISTANT! There is no "right" way to hyper, expose or process any film. Much of it is experimentation, and perhaps some luck.
Be prepared to go through a lot of film if you plan to become even semi-serious. In my case, I buy my 35mm tech pan in 150 foot bulk rolls, and 20 packs at a time in 120.
Hypering Times - this list is continually updated. use it only as a starting point. The information is based on personal experience and the experience of others. If you have any information of your own you wish to add or change on my list, I would love to hear from you. With your permission, I will add your times to this list.
-joe-