BTZS tubes with screens?

[John D Gerndt]

I have (read) heard that some people use fiberglass (window) screen between the film and the BTZS tubes in their developing process. Is this to prevent scratching, assist in loading or to get chemistry behind the base to wash away the anti-halation backing? Hoping to aviod doing something silly in the unknown (to me) process I thought I'd ask why it is done and for advice/data first.

Cheers,

[Jay DeFehr]

Hi John. I don't know about ULF tubes, but the ones I made for 4x5 use no such screens and work great. How's your big camera working out?

[Frank Lahorgue]

In my experience, different developers behave differently. D76 worked just fine, just fix long enough to remove anti-halation dye. Rollo Pyro was another matter -- it stuck to the inside of the tube. Several of us worked on solutions to the problem and settled on loading the film WET. Just dunk the film in a small tray and slip into the tube. Loading wet also saves time when you are running multiple batches; you don't need to dry the tubes before loading.

Good Luck --

[Andrew O'Neill]

Just load wet if you are concerned. I do and no problems. I find if I load film dry, the backs sometimes have subtle scratches. They don't show up in prints with a diffusion system. Don't know with a condensor though. Never used one.

[John D Gerndt]

Thanks guys,

I have been getting those scratches on the back and had trouble getting the film out too.

I will try loading the film wet.

I am so glad the solution is cheap and easy. Again, many thanks.

[Tim Curry]

This subject came up on a different forum and it seems to me there were two reasons for the screen.

First, it allowed the soultion to get behind the film and work to remove the antihalation backing more easily.

Second, it makes film removal much easier. By cutting the screen 1/2" longer than the film, it is simple to grab the screen's edge and pull it out. The film comes with the screen and the film's emulsion side is not touched, nor is the back likely to scratch as readily on a rough edge.

[Donald Miller]

I use screens on both my 4X5 and 8X10 tubes for the reasons that others have mentioned. Since implementing their use I have had no instances of film damage with Efke.

[j.e.simmons]

My experience has been the same as Donald's. I recommend the screens - cut 1/2" or so longer than the film. My screen came set with a curve in it from being rolled up since manufacture. I found it much easier to handle if I cut the screens so that the curve went in the same direction as the curved tube - in other words, the set curve in the screen goes in the horizontal direction.

[Brian Ellis]

Removing the film from the tubes can be difficult if you try to do it by grabbing an edge of the film and pulling it out while it's all the way down in the tubes. I've found it much easier to remove the film by putting the thumb of one hand (right hand for right handed people seems to work best) inside the tube and twisting the film with your thumb by applying pressure against the film and the side of the tube. The twisting motion will break the adhesion between the film and the tube and you can then slide the film up a little ways out of the tube with your thumb. From there it can be easily pulled out the rest of the way by hand. Takes maybe three or four seconds depending on just how stubbornly the film is stuck to the inside of the tube. Once you do it a few times you'll be able to twist and slide up simultaneously. I've found that way to be much easier and faster than trying to grasp an edge of the film while it's still all the way down in the tube.

Somebody mentioned scratches on the back of the film. I've processed hundreds of sheets of film in the BTZS tubes and never had a scratch. If you're getting scratches anywhere other than the top of the film I think it's safe to say you're doing something wrong unless conceivably there's some grit or something similar stuck to the inside of the tubes. If the scratches are at the top edge of the film they're probably caused by your fingernails when you try to grab an edge of the film to pull it out. If you use the method I've described above to get the film out of the tubes your fingernails never touch the film and scratches at the top will be eliminated.