Guys, don’t drop the ball. Go get your bag checked for leaking TODAY!

[sharktooth]

Go get your changing bag (dark bag) and check for light leaks, now. This is prompted by two incidents, one here about a year ago, and another one just recently over at Photrio. I’ll be posting about this on both sites.

https://www.largeformatphotography.i...n-my-negatives

https://www.photrio.com/forum/thread...d-film.201108/

In both cases, the changing bag was found to be grossly leaking light, but it took a long time, and considerable cost, to discover the primary issue. Like most people, I never considered changing bags to be a major problem, but in both these cases the changing bags were relatively new, so they were never suspected.

Testing your bag is very easy. You just need a bright flashlight to put inside your bag. With the room lights off at night, put your hands in the changing bag and turn on the flashlight. Move the flashlight around in the bag, and see if you can see any light coming through. Hopefully you don’t see any light coming through anywhere, but if you do, then those are leak points where light could come through to expose your film in unexpected ways.

It looks like changing bags have become very popular now with new film users, since you can develop film in a tank without needing a darkroom. With digital film scanning, this now becomes an attractive option for many people.

Over the decades I’ve collected several changing bags of varying size. I have one in my large format camera pack, to act as some camera padding, but also for emergency use if I need to load film holders in the field.

I decided today that I’d better check all my bags to see if they’re safe to use. The news was not good. The bag that I keep in my camera pack was leaking light at the zipper, and the material used in the sleeve sections was semi translucent. I found two other bags that were full of leaks and should never be used, but they looked fine cosmetically. I found a couple of bags that had a few pinhole leaks that could probably be O.K. in a darkened room, or could possibly be patched. Fortunately, I did find a few good ones, and I’ve put them in plastic zip-lock bags with the date tested. Age is not the primary consideration. Only one bag that I have has a manufacturer’s label. That one was a very large Burke and James bag that was still light tight. That one had to be as old, or older, than me.

One thing that I was shocked to discover is that only one of the layers is light tight. I thought the double layer bag was a safety measure to protect light leaks if one layer goes bad. This is NOT the case. In every single bag I checked, one of the layers is a very thin woven material that provides no light protection at all. I can see the whole flashlight through it. It’s about as effective at blocking light as a one stop neutral density filter. I couldn’t believe it, but that’s the way they’re all made.

Anyhoo, film is too expensive these days to be farting around with, so go check your changing bag.

[Martin Aislabie]

I replaced my Harrison Changing Tent last year - due to light leaks.

Same method.

My light leaks were from the joints of the arms in to the tents.

Everything else was fine - as far as I could tell.

The Tent was 10 years old - not bad I think for something that has seen quite a lot of use.

FWIW - I have always used my Changing Tent in subdued lighting.

Martin

[Photopham]

whats a good brand for NEW darkbags? I bought new one last year that had a zipper failed so im looking for suggestions.

[Tin Can]

Back when I joined this forum EVERY USED CAMERA came with a moldy bag

I have never used any bag

And I threw them all out

Germs

[LabRat]

Was assisting on a pro shoot long ago, loading holders in the back of a car with sunlight pouring in with the pro's krappy old bag on a car location shoot, and several chromes had weird fogging here and there, and I was getting blamed for it... I said I followed his instructions exactly, but the bag had obvious leaking issues, and even with any bag, I preferred to load film in a cool, dark, quiet place, undistracted, not sweating, and no time pressure... He replaced the bag shortly after shoot, but sat over me back at the hotel room up/down loading, watching me like a hawk (through the bag???) to make sure I was doing it right (but being distracting)...

Came out fine... ;(

Steve K

[sharktooth]

After an episode like that, I'd probably be looking to bag a new job.

[sharktooth]

… another cross posting with Photrio

When the inimitable Drew Wiley posted about using a plastic garbage bag as a changing bag/tent liner, this got me thinking. No, I wasn’t thinking Drew was nuts, I was thinking about another similar plastic material that I was planning to experiment with for bellows.

A while ago, I’d been doing a search for different light tight materials that could be used for making bellows. I perused fabric stores with my trusty flashlight in search of something “cheap” with potential. I eventually found something promising at Home Depot. It was Roberts 6mil Polyethylene Film for laminated and engineered wood flooring. This is a black plastic that is light tight, and is a bit thicker than a garbage bag. It’s designed to be used as a moisture barrier under wood flooring, so I’m assuming it has some decent durability as well. The good thing is that it is relatively thin and flexible at 6mil (0.15mm) thick, comes in a large roll (10 ft x 12 ft, or 3.05m x 3.66m), and is relatively cheap.

I haven’t used this material to make a bellows yet, cause bellows are hard, and procrastination and stuff, but I did muster enough energy to try this on some leaky changing bags ….. with success!

As noted in my original post, I have several old changing bags, so I’ll outline here some of the key construction points, to help with potential repair or salvage. All the bags were made with two separate individual bags that are joined together. I’ll call these the “inner bag” and the “outer bag”. Both bags are made of a woven cloth material, but only one of these bags will have a light proof coating over the material. I’ve also discovered that the light tight coating is only applied to one surface of the material. In all the samples I have, the light tight coating is applied to either the outside surface of the inner bag, or the inside surface of the outer bag. This means that your hands won’t contact the coated surface during normal use.

The inner and outer bags cannot be joined together at the zipper end (or you couldn’t get inside), but they aren’t completely joined around the remaining perimeter. They are usually just joined together at a few spots, like the sides at either end of the zipper, and somewhere around the sleeves. I think the joining is minimized, since it’s not really necessary and more stitching leads to more potential for pinhole leaks.

If the coating starts to crumble or chip off, the loose pieces will end up in between the inner and outer bags. When you open the zipper on the outer bag, you can shake those pieces out. If you get a lot of stuff falling out, then the bag is probably unsalvageable, and should be tossed. If you have no significant loose debris, but there are still small light leaks, then you can probably use this plastic to repair the bag.

Here’s what I did for the repair of a leaking bag. Open the zipper for the outer bag, and pull the inner bag out (basically turning the outer bag inside out. Do this gently, and try not to force anything. Things will look a little strange, since you have two bags joined together inside out. The key here is to identify the coated surface. You want to cut out a piece of plastic to cover as broad an area of the coated surface as possible. It doesn’t have to be perfect at all. I used Gorilla tape to join the plastic pieces to the coated surface. The tape doesn’t need to be around the whole perimeter, but just enough to keep things in place. You can add more Gorilla tape around the seams if you want. Once that’s all done you can turn the bag out the right way again. This tends to be more difficult, since the plastic adds a bit more stiffness, but it can be done if you take your time. This worked well for me.

On another bag I used this plastic sheeting to make a “flap” to fold over the zipper, since that was a leak point.

… and on a related note, I think this stuff would probably work well as a temporary light blocking cover for windows and door frames, to make a temporary darkroom. You could hold it in position with gaffer’s tape.

[Drew Wiley]

Sharktooth - put a strong flashlight into that and you'll might see some light, even at 6 mil. It's also easy to get small puncture marks in it. But I do use 6 mil black polyethylene roofing rolls to black out my removable fiberglass darkroom partitions. I do permanent walls too. But two partitions are designed to be removable if necessary. The thick black plastic bags that black and white printing paper comes in seem to be even thicker than standard 6 mil, and might be better. But either way, a drymount tacking iron can be used to heatweld polyethylene seams. Use silicone release paper in between the iron and the plastic when doing it.

Gorilla tape simply won't adhere for the long haul. It's only good temporarily in this case. The only tape that is really permanent is an expensive red 3M tape expressly made for long term polyethylene applications. But ordinary cheaper red Builder Tape by Intertape would be a reasonable substitute. But both are thin, somewhat translucent, and tear relatively easily. It's better to try to heat weld that kind of sheet material together.

The disposable black liners which I use inside film changing tents is only about a third a mil thick. But I do have some set aside fully rinsed out thick black bags from 20X24 printing paper boxes which should work great as a changing tent by themselves, not during the daytime per se, but with at night. That strategy has worked for others before, as an ultralight ultra-portable option. A couple of simple flexible wands in an X pattern would retain a tent shape. Sure beats what Ansel Adams did in his younger years, changing out his film holders inside his sleeping bag at night. I've seen a professional print retoucher at work on some of the results decades later - a task synonymous with Purgatory.

[sharktooth]

Drew, where do you find silicone release paper? I don't have any drymount equipment, but I might be able to do something similar with a flat tip on a temperature controlled soldering iron.

I've checked the light fastness of the polyethylene with a flashlight in the darkroom, but it's obviously made to a price point, and small defects wouldn't be surprising. Since I've installed it in between the inner and outer bags while inside out, the Gorilla tape is really just holding it together for the outside in reversal. Once that's done, the Gorilla tape doesn't really matter that much since the plastic doesn't really have anywhere to go, because it's constrained between the two bags. I'd say it's about 90% effective, so the original bag shouldn't be too far gone to start with. It's just cheap insurance.

I guess the best approach is to just assume that any changing bag is suspect, and use it only at night or in a very dark room. If it needs to be used in bright daylight, then do whatever you can to provide as much additional shielding as possible. In a darkroom, you can literally "see" when there are problems. With a changing bag, you can see everything except problems.

[Drew Wiley]

Or baking paper. Something non-stick, but which won't melt and leave a residue. Not ordinary wax paper. But drymounting irons ordinarily are Teflon coated, so it wouldn't be too hard to scrape residue off if it gets stuck to the iron. Or you could use a heat-bagging sealer like used for freezing vegetables etc, and commonly available. U Line would have a selection of heat sealers, along with all kinds of poly bags.

The trouble with most cloth tapes, whether Gorilla Tape or Gaffer's tape, is that even the edges are sticky and some of that will transfer to your tent wall, or maybe even your fingers. I don't have any real book tape laying around to test. But polyethylene resists most adhesives.