Mercury Hypersensatization

[Stephen Frizza]

I am curious about an article I read recently which was published in 1940.
it talks about a process of hypersensatizing emulsion with mercury.
the process stated if that if you get a roll of film, a container and a drop of mercury and seal the drop of mercury and the roll of film in the container for one week (making sure not to let the mercury come into direct contact with the film) that mercury vapor with hypersensatize the film increasing its speed by 3-4 stops. does this work with modern emulsions? has anyone tried this?

 

[Ian Grant]

There were a lot of Hyper-sensitisation techniques around at one point, astronomers in particular used them, but they worked best with older film emulsions. Some like Hydrogen Peroxide worked before or after exposure, and sulphur dioxide, metabisulphite etc are used as well, but these films used active gelatins.

Modern film emulsions use traces of Gold etc to latensify emulsions, control the sulphur content by adding thiosulphate to de-activated gelatin for optimal sensitivity and this is done in a far more controlled way during emulsion manufacture which give a film that's stable at higher speed. These films are mucj less sensitive to hypersensititisation.

Ian

 

[Robert Budding]

I was trained as a chemist, but I wouldn't use mercury at home because I don't have adequate ventilation. And I've worked with some really nasty chemicals, such as HF. (I do have two kids and a wife present.)

 

[greybeard]

I remember my father describing this technique to me in the 1950s; he learned it in the Army Counterintelligence school. When "fast" film was ASA 100, it was probably pretty useful. There was also a technique of pre-exposing film to move shadow detail up on the characteristic curve, thereby increasing the "effective" film speed. I did play with this, but found that it has a pretty limited application

I can't recall whether it was to be done before or after exposure, but I suspect the latter. It may not work on modern fast films, but it would be interesting to try. As long as the (very small) drop of mercury stays in the box, the hazard is minimal, because the vapor pressure at room temperature is miniscule. Disposal of the remainder is best accomplished by reacting it with sulfur (see your local garden center...) before final disposition.