What the...! Luminous tape on 120 film?

[L Gebhardt]

Yank it hard enough and you might give yourself an X-Ray

http://physicsworld.com/cws/article/news/36357

Though admittedly they were cannoning that roll of scotch tape through the machine at quite a rate of knots

Luckily it only works in a vacuum, or we might be getting cancer.

 

[PeterB]

Cool. I saw this last night too. I went back to check my previously processed rolls of film and sure enough the image of the luminescence (mottled light grey) is clearly visible at the end of a roll of 120 of film (HP5+).

Now if my negative pressure ventilation system approached that of a vacuum, the process would be generating X-rays too ! Huh you say ? Well, check this out.

 

[paul ron]

I'll second tearing the tape instead of trying to peel it.

Frank thanks for the wiki, I knew it had a name.

 

[Augied]

I've witnessed this too. I worry about leaving the tape on the film. I've been told that it could loosen and migrate to more important parts of the film, so I just peel slowly.

 

[PeterB]

I take the tape off after I've spooled the film onto the reel. I do this because I don't like the chemicals seeping under the tape and not being fully rinsed out in the last step. My last step is four fill and dumps with progressively more inversions between each f&d. Also I don't like the feel of peeling off soggy tape !

I wonder why peeling off the tape would only emit x-rays in a vacuum and not at atmospheric pressures.

 

[Bill Burk]

I peel slowly and hit the film that was under the tape with a sensitometry test. I figure the bigger risk is scratches during this handling.

 

[PeterB]

Bill, what do you do with the density measurement of the processed film under where the tape was ?

 

[Vaughn]

This is something I have noticed for years -- though I also assumed it was static. I find that it does usually expose the film, but just right where the tape was stuck to the film. In theory, that end of the 120 roll should have no expose and be blank. But when I have noticed the light generated by removing the tape, I have also noticed some exposure density on the film only where the tape was...sort of a ghost image of the tape.

I have a bunch of 120 to develop...several different brands (Kodak, Ilford and Fuji). So I will do a little experimenting with tape removal! Film at 11

 

[Dennis S]

Wow very cool post. Now where did I put those Wint O Green Life Savers? Never a dull moment @ APUG. Film & Physics all in one day. Maybe I will get a chance to thrill someone soon (besides me) in the dkrm.

 

[Svenedin]

I have noticed this too (a green flash) and finally did some searching to find out what it was (and found this thread). I will post a picture of the tape end of a piece of developed 120 film. The triboluminescence has actually exposed the area of film where the tape was. There is also a small area of fogging but this area of the negative was blank anyway so no harm was done. Interesting.

 

[Gerald C Koch]

It is what is called 'silent discharge." Whenever two surfaces are separated there is an inegquality of electrons on one. It is a serious problem in say newspaper printing where the discharge can be quite high from the paper rolls. It is also what makes Saran Wrap work. The film is not sticky in itself. If left for a few days the attraction dissapates and is lost. I have seen its darkening of the film but this is not in an image area.

 

[AgX]

It is what is called 'silent discharge." It is also what makes Saran Wrap work. The film is not sticky in itself. If left for a few days the attraction dissapates and is lost.

Saran and similar foils (based on PVC- or PE-compounds) adhere mainly due to van der Waal-forces, not eletrostatic charge.

 

[voceumana]

I've also seen this when pulling up a polyester blanket up from my bed in the dark. I think it's one reason I don't like polyester blankets very much--not the luminescence, but I can "feel" the charge against my skin.

 

[darkroommike]

Triboluminescence some wintergreen candies do this too.

 

[Gerald C Koch]

Saran and similar foils (based on PVC- or PE-compounds) adhere mainly due to van der Waal-forces, not eletrostatic charge.

However the stickiness disappears after a while. This would not be true for van der Waals' forces.

 

[RalphLambrecht]

It's called triboluminescence. See this wiki

wow; learn something new every day on APUG.

 

[bernard_L]

Like PeterB, I prefer not to leave the tape doing whatever with the process chemicals. I've noticed it's not as bad if removed slowly, like Bill Burk states; possibly the opposite charges have time to neutralize by conduction. And, I could be wrong, but it seems that it's not as bad as when I was younger; so: (1) manufacturers noticed and improved their product; (2) at least that is better than it used to be

 

[Svenedin]

Like PeterB, I prefer not to leave the tape doing whatever with the process chemicals. I've noticed it's not as bad if removed slowly, like Bill Burk states; possibly the opposite charges have time to neutralize by conduction. And, I could be wrong, but it seems that it's not as bad as when I was younger; so: (1) manufacturers noticed and improved their product; (2) at least that is better than it used to be

I also like to get rid of the tape. I don't want any chance of it contaminating chemicals with glue or whatever. It has to come off anyway because it stops the film dripping properly when hung up to dry. I prefer to cut it off with scissors. I know some people fold it over to provide a firmer edge to load on reels. I guess whatever works for different people is the way to do it.

 

[bdial]

The tape doesn't cause any problem for the chemistry, at least that's been my experience for the past 45 years or so.
I tear the tape at the interface between the paper and the film, when drying I put the tape side up and trim off that end when the negs are dry and I sleeve them.

It's fun to see science in action when you tear it in the dark and make the little spark.

 

[MattKing]

I'm with the "fold over to make the edge stiffer crowd".
And I cut the taped part off as I put the film into the Photo-flo.
Vive le difference!

 

[David Brown]

... It's common, it's normal, it's harmless, ...

The tape doesn't cause any problem for the chemistry, at least that's been my experience for the past 45 years or so.

I'm with the "fold over to make the edge stiffer crowd".

I love threads like this. Besides the fact that the OP is 8 years ago, each new person that witnesses this thinks they've discovered something.

Can one imagine that if this truly were a problem, it would not have been dealt with in the more than a century that roll film has been around and the millions (10s of millions?) of 120 rolls that have been shot and processed?

 

[pentaxuser]

OK. I have just seen this thread and here's another mystery. There is a line through the middle of the OP from the words "just a glow.... " to the end of the message. I have never seen this before and yet no-one else makes any mention of this line.

pentaxuser

 

[Sirius Glass]

I'm with the "fold over to make the edge stiffer crowd".
And I cut the taped part off as I put the film into the Photo-flo.
Vive le difference!

Me too.

 

[MattKing]

OK. I have just seen this thread and here's another mystery. There is a line through the middle of the OP from the words "just a glow.... " to the end of the message. I have never seen this before and yet no-one else makes any mention of this line.

pentaxuser

You mean like this: Mares eat oats and does eat oats and little lambs eat ivy...?
Highlight the text you want struck-through, and then click on the "+" in the line of formatting and other options above where you enter text. Strike-through is one of the options.

 

[Sirius Glass]

You mean like this: Mares eat oats and does eat oats and little lambs eat ivy...?
Highlight the text you want struck-through, and then click on the "+" in the line of formatting and other options above where you enter text. Strike-through is one of the options.

Hey, these instructions actually work!