View Full Version : Silly question about vinegar-based silicone interacting with film, and light leaks.

5-Jan-2018, 17:29
I'm probably becoming the most annoying guy on this forum with my paranoid questions.

But really, I don't want to mess things up 'cause I'm going on a trip that's kinda expensive for my pockets and yeah.

So I have a box where I store my film holders. It's padded with silica gel pockets, so moisture has no way with my film.
This box also happens to be transparent, and while I was taking a pinhole long exposure the other day in my darkroom (which was now lit by a 800W tungsten bulb) for a whole half hour, I had the box about 10ft away from the light, directly exposed to it.
Film holders were stacked, but I don't have enough experience in the field to know if that completely fogged that particular film or it did nothing to it.

The other issue I have is, this box didn't have a nice seal, so my father thought putting some silicone around the edges in that small groove could create a nice rubbery gasket. Fair enough.
I let the lid dry for two days, put it on, now after a day or so I open it and the excessive smell of vinegar comes out of the box...
I know Fixer is basically pure vinegar of some sort, and I hope by the thick vinegar air in the box that maybe the fixing process has started on absolutely blank film?

I'm just 18, paranoid and anxious to go to where I'm going to shoot some landscape on my 4x5" camera. Please don't go too hard on me.

PS: I have 5 film holders, 3 loaded with 6 sheets of Ektar, 2 loaded with 4 sheets of HP5+, just in case anyone wonders, and 4 are Fidelity and one is Toyo.

5-Jan-2018, 17:40
Film holders are light-proof. There is no reason to be concerned if they are exposed to light.

5-Jan-2018, 17:44
Oh that's just what I want to hear! A breath of ease, since that kind of solves the issue of the silicone since if not even light can enter it, then I shall forget of the thick air of the vinegar-based silicone.
Guess that was easy to solve, just needed reassurance form someone with experience in the field.

5-Jan-2018, 18:26
Stop bath is closely related to vinegar. Fixer is a whole other chemical. No need to worry about the fumes from your RTV silicone sealed corners.
I am curious to know if RTV silicone is inert in the presence of developer and fixer, as I would like to make my own developing tank for 5x7. I will most likely just try it and see. For me, experience is the best teacher. I suspect as you experience more and more, your questions will only get better and better.

6-Jan-2018, 00:28
A new, or good-condition, darkslide is lightproof. An old secondhand one might be less secure, or it might be fine. Testing using enlarging-paper in full sunlight for a few hours, moving the filmholder to vary the angle of light, is cheaper than testing with film -- or not testing at all and having an unpleasant surprise.

Stop-bath is acidic in order to stop quickly the action of alkaline developers. It doesn't have to be based on acetic-acid (vinegar), though it often is. The odourless stop-bath products are usually (always?) based on ascorbic-acid and it is possible to make your own single-session stopbath by dissolving the ascorbic-acid powder from 'healthy' shops etc. in plain water.

Rapid-fixer is made of several chemicals, frequently including acetic-acid to maintain the life of the fixing agent when a potentially alkaline-developer filled piece of paper is plunged in to it. Odourless fixers also exist, as do neutral-pH fixers, so there are variations in the constituents and acetic-acid is not necessarily always found (or smelled).

The action of fixer is to remove the undeveloped silver-halides from the emulsion, leaving behind the developed silver image. Acetic-acid will not do this, and that is not it's purpose in either stop-bath or the various formulations of fixer.

6-Jan-2018, 06:59
Stop bath is closely related to vinegar. Fixer is a whole other chemical.

Thanks for pointing this out. Stop bath and vinegar are the same thing -- just a 4-5% solution of acetic acid. Apple vinegar has a reddish color while white vinegar is just acetic acid with out it. Yellow stop bath has a PH indicator added.

If you added anything like silicone to your film holders you are actually INCREASING the chance of light leaks. They are made to be light tight, and dust, dirt, or anything -- including silicone -- will make a good seal more difficult. Your admitted paranoia has gone too far, unfortunately. Sure, film holders can leak if they are damaged or old, but it's easy to test them without resorting to extreme measures -- as Martin has pointed out. Then, if one is leaking, you can try to fix it and retest -- or just get a new one.

Rick A
7-Jan-2018, 06:46
That "vinegar" smell from the silicone is the vulcanizing agent that allows the caulk to cure once it is exposed to the atmosphere(O2). It's annoying, but harmless, and will dissipate in a few days.

7-Jan-2018, 07:30
That "vinegar" smell from the silicone is the vulcanizing agent that allows the caulk to cure once it is exposed to the atmosphere(O2). It's annoying, but harmless, and will dissipate in a few days.

The smell is Nitric acid (HNO3), a highly corrosive mineral acid.

Drew Wiley
9-Jan-2018, 19:26
Silicone is relatively inert compared to other options, but you do need to let it fully outgas first. Preferably use a solvent-free aerospace grade silicone next time.

9-Jan-2018, 21:17
The acetic acid released will generally not harm most materials, but for corrosion prone metals (like copper), there are other sealants based with acetone (but these can harm plastics/paints)... They are sold for sealing auto engine sensors, hi-voltage sealing, etc

You can also try acrylic paint...

Steve K

Drew Wiley
10-Jan-2018, 18:15
Paint can take weeks to outgas. Line the box with black cardboard or just buy a black box to begin with, if this is a real issue at all.

John Kasaian
10-Jan-2018, 19:52
I keep my film holders in zip lock plastic bags, Brawny brand, or similar. This guards against invasive dust and moisture and is inexpensive.
I like to keep my film holders in the dark in case leaks manifest themselves---unlikely but it's a belt and suspenders approach. There are plenty of lunch box size soft sided coolers than can digest 4x5 film holders. If you need a hard box consider a cooler like Coleman or Igloo. These may attract bears( the ones in Yosemite apparently can read) but it won't attract thieves like a real live camera bag