How many turns make 120 light-tight?

couldabin · Jun 30, 2015

I have never used 120 film (35mm and large format only) and am making a camera that will take short (as little as ~10") lengths, which I'll make up in the darkroom. I plan to use a paper leader/trailer only (220-style). How many layers of paper are considered appropriate to ensure light protection on the spool? Also, where would one go for spare 120 spools?

Thanks.

duane

Rick A · Jun 30, 2015

I measured a backing paper, 15 inches from where the shoulder of the paper squares to the lead edge of the tape, plus 10 inches of paper after the film to where the taper starts.

Xmas · Jun 30, 2015

Obtain (a) scrap 120 backing paper from friendly local lab... Free.

PCC · Jun 30, 2015

couldabin said:
Also, where would one go for spare 120 spools?

If you have a camera store near you that processes 120 film then you can ask them for spools. The local stores to me that do this just toss them into the recycle container after pulling the film from the spool.

gone · Jun 30, 2015

If you don't have a photo store nearby that has spools, I have spools. Just PM me w/ your mailing address and I'll send you a few gratis. No backing paper though, I always threw it away.

Jeez, I hate to think how much money it cost me to get these w/ the film attached (this is just a few of the spools around here). If you shoot medium format, spools are like Tribbles. They seem to multiply on their own.

mwdake · Jun 30, 2015

I have plenty of 120 spools with backing paper if you need any I can send you some.

ic-racer · Jun 30, 2015

How many mils tolerance are you cutting the paper? How carefully are you affixing the paper to the film so it is aligned? Brand name 220 leaks light in direct sunlight. You will have to experiment to see what is acceptable with your system.

couldabin · Jul 1, 2015

Thanks for the quick responses. An APUG member will be sending me a few spools, which should be enough for this project. I promise to post images if it works ... (and an explanation if it doesn't)

couldabin · Jul 1, 2015

I'm hoping to use 120 backing paper so I don't have to cut it for width. I'm planning on creating a layout jig of some sort for my darkroom counter that will hold the paper and film in alignment. I'm imagining a great deal of potential for damaging the emulsion ...

ic-racer said:
How many mils tolerance are you cutting the paper? How carefully are you affixing the paper to the film so it is aligned? Brand name 220 leaks light in direct sunlight. You will have to experiment to see what is acceptable with your system.

tessar · Jul 1, 2015

I'd expect six turns to be more than adequate, but you can a;ways give it a couple of extra turns just to be safe.

couldabin · Jul 2, 2015

And there should be more room on the spool for extra-long ends, since there is no backing for the length of the film, yes?

How many turns make 120 light-tight?

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