Hoffman Camera Co. 8x10 vacuum holder how to?

[Chris Gardner]

Hello,
This is the first time I have listed a question in this forum so please accept my greetings. I have searched the forum archives for info on vacuum film holders and did not find my answer there so...

Does anyone have personal hands on experience using Hoffman 8x10 vacuum film holders? I purchased several in anticipation of my own need, but I am a little uncertain as to what I should use to create the suction. A metal tube sticks out between the dark slides. Can I use a bulb with a lock like a blood pressure gauge? A bulb will push air in, but when I start to let go it would suck air back in pulling the film tight, no? I need a setup that will hold its suction for extended exposures. Was there an original configuration that would have come with the holder?

It should be noted that I want to work in the field, possibly at night, and would not consider an actual vacuum pump like a darkroom easel would use.

I have the Hoffman Camera Co.'s info, but I wanted to ask here first to see if anyone had used the holders first.

[David Van Gosen]

Automotive tool supply houses have a pliers-style vacuum tester that may do the trick.

[tor kviljo]

I have used the Mamiya RB 70mm roll film holder that have vacum-assisted film-flatness. On this one, you use a rubber-ball the same type you use for blood pressure test, and as you note: the ball creates the vacum when first pressed together and then let free to inflate by its own tension. On the Mamiya rubber-ball, there is a valve to release vacum so that film is not sucked strongly towards pressure plate (possibly creating scratches) when moving to next frame, on a sheet film back, that feature should be unneccesary as vacum will cease in a short while. Linhof also made vacum sheet film holders (as well as motorised-vacum-assisted roll film holders for aerial cameras), and they look (I have never had oportunity to handle one) like ordinary sheet film holders & looks to have a similar small rubber ball to produce vacuum as the Mamiya back.