Lately I've been asking a lot of questions about light leaks and replacement bellows for my Sinar 8x10. Someone else had posted something about "the most permanent" tape to use for bellows. This got lots of varied response, but the idea that seemed likely to me came from Jim Jones. In that thread, he suggested scrubbing acrylic paint into pinholes and that it seemed to make for a good, permanent repair. Good idea Jim!
For those of you who might be interested, here's the procedure I used. While this was just completed last night and hasn't yet been "field tested", I have a fairly high level of confidence this will be a lasting repair.
The majority of the light leaks in my bellows was at the rear frame where the bellows attaches. There had already been some "duct tape" type stuff applied to part of the frame, over the joint where the last fold of the bellows is attached to the frame, but I did something better. I have some heavy (0.006") black vinyl "pipe tape" we often use at work, that has a great adhesive and doesn't leave a lot of goo behind when it's removed. After cleaning up the back frame / bellows junction with alcohol, I applied 4 strips of this tape around all four sides, with some contact cement used for enhanced adhesion and permanence. The contact cement was of the acetone solvent variety, so it dries quickly and isn't nearly as goopy and difficult to work with as typical 3M 'rubber' contact cement. It's also lower in viscosity and can be applied sparingly with a small model paint brush. I applied the contact cement to the bellows where the tape was to go, and also to the adhesive side of the tape. It only need a minute to two to get tacky and the only catch is, once the two parts (the tape and bellows frame) are mated, there's not much time for repositioning. Care is needed here and it helps to 'dry fit' the tape strip first, before cementing in place. This took care of the worst light leaks at the bellows rear frame.
There were also a number of pinholes down the length of all four corners at the folds in the pleats. None of these were bad and I doubt were much affecting film fogging. In addition to that, they only appeared at full extension. I've been using wide lenses, so probably would have never noticed them without the careful flashlight checks I did with the bellows maxed out. Anyway this is where Jim Jones' great idea comes in. I went to Michael's craft supply and started looking at acrylic paint. There are many many kinds and types of acrylic and it turned out (don't ask me how this happened) that there was a gal there who was actually KNOWLEDGEABLE about acrylic paint! I told her what I was trying to do with it and it appeared she actually understood and didn't give me the "you're from Mars aren't you?" look when I told her this was for a camera repair! She pointed me to a Liquitex brand of professional acrylic paint, made for canvas and fabrics which is waterproof when dry, has latex (rubber, yes!) in it and stays flexible indefinitely and is supposedly very durable and tough as nails. How she knows all this, I have no idea, but she certainly had me convinced and my BS detector didn't so much is twitch. So I'm wandering here, sorry...
I cleaned up the corners of the bellows with alcohol and a swab and liberally brushed on the paint. You have to use judgement here, too thick is bad and could interfere with the proper folding of the bellows. I made sure I covered 100% of all the little creases and folds in every corner of every pleat down the length of all four corners of the bellows. I didn't worry too much about neat, clean edges when painting. It's really hard to even see it when dry. Jim Jones suggests "scrubbing" the paint in with a toothbrush on the INSIDE of the bellows, which would probably be a more thorough way of doing this. I considered doing that and, No.1: The fabric on the inside of the Sinar bellows doesn't look too friendly to this method and, No.2: It would have taken hours and hours and hours of frustrating work to do, plus I was worried about the bellows folding properly afterward. So I painted it on the outside. This acrylic material appears to adhere very well on the outside of the bellows and now that it's had the chance to dry, with the bellows at max max extension (the paint should also be applied in this position) this morning when I look at it, it's hard to even see the paint without a bright light.
I removed the bellows after making sure the paint was completely dry - gal at Michaels says it takes four hours, I gave it 12 - and folded and flexed the bellows several times. The pleats fold up nicely and while there is a tiny bit of "paint tack" noise from the fresh paint surface when opening the bellows, it's not bad and doesn't give the impression, or look like, the paint is sticking together or adhering to adjacent painted pleats, as I feared it might. We'll see how it works when the bellows have been tightly folded in a hot car for a few hours, but I'm pretty sure no matter when happens there, the pinholes will be plugged up for a good long time.
I plan to leave the bellows extended and give the paint another day to completely cure, but so far, the flashlight test does not reveal even the slightest, tiniest pinhole or light leak anywhere. And I happen to have one hell of a powerful flashlight! Looking into the bellows through the front under a dark cloth and with a film holder in the back, I used to see 'stars' everywhere. Now I see NOTHING but Stygian, pitch black!
So please forgive my usual wordiness (not the first time I've said that) but I wanted to share this successful - so far - repair with anyone else contemplating dropping $300+ that they might not have at the moment on new or custom bellows. I'll report again later, after I've had a chance to put this repair work through a little torture testing in the field, but I'm pretty confident I'm quit of my light leaks for now.
Last note as a disclaimer: This repair was done on my Sinar OEM bellows, which appear to have an outer covering of rubberized vinyl or something. I'm not sure how well this would work on old leather, or other more porous outer bellows materials. In your particular case, depending on your bellows materials, it might make more sense to do this repair from the inside, per Jim Jones recommendation.
The acrylic paint I used is: "Liquitex BASICS, Mars Black". The contact cement used for the tape on the rear frame is: Beacon "527" Multi-Use Glue, which is not technically "contact cement" but works well in that capacity. I might have preferred a black, non-adhesive fabric type tape, but I wasn't able to find anything like that. I think the heavy vinyl tape I had will make for a durable substitute. I don't know the make of this tape, I think we have it custom made to tell you the truth.
So, if you need to repair light leaks or pinholes in your bellows, here's one way that seems to work well. Good luck!
Cletus
Reply With Quote
Bookmarks