static discharge in 120 film.

[fidget]

When I popped into a darkroom to put a couple of 120 rolls onto spools, I had a surprise. As I separated one roll from its backing, just as I got to the end of the film where the film is taped onto the backing, I saw a luminous blue strip, apparently between the film and backing. It looked like a steady discharge rather than a sudden spark. I didn't pull the two apart quickly. The film was an out of date FP4+ roll given to me for use as a simple camera test roll. I can't say that the negs suffered, but they all had a mottled appearance which I thought was due to other things as all frames showed it. From training received for anti-static precautions in the handling of semiconductors, I remembered that high voltages can be produced even without any visible signs of discharge. Can this be a problem?

 

[Ole]

Was that when pulling the tape off?

If so, what you saw was triboluminescence. It's a "feature" of sticky tape, and not strong enough to fog the film except possibly just under the tape. I think Ilford has changed the tape in recent years, I seem to remember much brighter light in the past.

 

[Denis P.]

Yup, had that happen to me once. Wintertime, I think. Central heating was on, anyway...
I saw it as I was removing the tape from the film...

Ruined the last (and the best) shot on the roll.

Needles to say, after that I remove the tape very slowly and carefully.

Denis

 

[glennfromwy]

I don't peel the tape off any more. I tear it in half at the juncture of the film and paper. I've never had the discharge harm anything, I just don't like it.

 

[konakoa]

Happens all the time with my 120 film. Doesn't harm anything, just leaves the edge under the tape slightly fogged where the tape was. Kind of fun really. Scotch tape in a dispenser will do the same thing as you peel it off the roll.

 

[jim appleyard]

I always rip the paper off the tape, not the film. Never had a problem.

Loading film is easy. After awhile, you get so good at it, you can do it with your eyes closed. (That's something I used to tell my students. I don't think any of them ever got it)

 

[Alex Hawley]

Its just a completely normal thing. Its been there for many years. Harmless.

 

[MVNelson]

humidity or lack there of will have a lot to do with this. I cut the tape film juncture very slow and careful. In a very dry darkroom with very quick movement the static light source can be pretty bright.

 

[buze]

I had that sort of light happen when forcing open an envelope of 4x5 sheets tho (forgot the cisors, anyone ?).. Scared the hell out of me at the time, luckily there was an inner envelope..

 

[Ole]

humidity or lack there of will have a lot to do with this.

It's not static, it's triboluminescence. And it's independent on temperature and humidity. The main variable is the glue type used.

 

[Fotohuis]

Correct, with the remark that Fujifilm has on all their 120/220 roll films a very nice type of tape which is without any of these kind of problems.
Also all their newer films are equipped with a self adhesive tape to 'lock' an exposed roll film. Nice service!

Best regards,

Robert

 

[skahde]

It's not static, it's triboluminescence.

Yep, here is more about it: http://en.wikipedia.org/wiki/Triboluminescence

best

Stefan

 

[fidget]

Thanks for the answers, I'm not alone!
In my case, I saw the light (no pun intended) when I was still separating the film from the backing, before I removed the tape from the backing. I will be careful in future.