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Tape sparks


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#1 Jimmy Browning

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Posted 08 August 2007 - 02:27 AM

I was loading some mags in a darkroom recently and noticed something odd. As I took the tape off the end of the raw stock, I could see what appeared to be a bit of electricity at the contact point where the tape was peeling off the film. just a very very thin line at the contact point. I thought at first maybe it was because I was taking the tape off a little too fast, but on the next roll I went very slowly but with the same result.

I'm used to changing in bags and tents normally so this is the first time I noticed this phenomenon. Has anyone else ever observed this? Is it normal?
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#2 Nick Mulder

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Posted 08 August 2007 - 03:09 AM

http://www.cinematog...n...7&hl=sparks
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#3 John Sprung

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Posted 09 August 2007 - 02:19 PM

I was loading some mags in a darkroom recently and noticed something odd. As I took the tape off the end of the raw stock, I could see what appeared to be a bit of electricity at the contact point where the tape was peeling off the film. just a very very thin line at the contact point. I thought at first maybe it was because I was taking the tape off a little too fast, but on the next roll I went very slowly but with the same result.

I'm used to changing in bags and tents normally so this is the first time I noticed this phenomenon. Has anyone else ever observed this? Is it normal?

Yes, it's quite normal and harmless to see this when you pull adhesive tape off in total darkness. The much bigger piece of tape around the outside of the can may well show you even more light.

Static becomes a problem when it happens due to the unwinding or re-winding of the film itself. In the old days, it was such a big problem that the original name of the ASC was the "Static Club" -- it was the biggest problem cinematographers had in those days. It would look like lightning flashes on the screen.

If you have rewinds in a darkroom, you should ground them, and have a conductive grounded floor mat. If the humidity is low, spritz the place with a 50-50 mix of Downey fabric softener and water. Its anti-static property is designed to keep clothes from exhibiting static cling, and works fine for protecting photographic film and electronic stuff, too.

BTW, the adhesive tape thing may be a chemical phenomenon, not static electricity -- I'm not sure. There are some substances that can turn mechanical energy directly into light, but they're very inefficient. You have to hit them with a hammer in total darkness to see a little flash.



-- J.S.
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New Pro Video - New and Used Equipment

The Slider

Glidecam

Paralinx LLC