View Full Version : Chemical Residue and Neutralising unwanted leftovers in Darkroom??

3-Sep-2017, 00:31
Hi all,
I have been at the gelatin in a small dark room on and off for roughly 30 years (only B&W that is). Up until pretty recently I have never paid much close attention to the chemical side of things apart from simply buying shop-bought mixtures for the products I have used, and kept different trays/jugs for the main 3 components etc. Basic stuff.

2 years ago i 'discovered' FB paper, I got hooked on the Gloss and finish of Ilford MGIV and warm tone papers, so pretty much only using FB paper, and certain things are changing as a result;
- Have started making my own washaid,
- My sizes are creeping up and I am spending a significant amount of time and money on each print
- Have started selenium toning

I am starting to notice small things about cross contamination and things chemical in the darkroom, basically I am paying way more attention.

I got to thinking today about my methods of mixing chemicals, segregating trays, mixing jugs and also have noticed residual chemicals causing crystalisation, and wondered about the following as it relates to a BLACK AND WHITE process; (apparently B&W is tame compared to colour hazard or contamination wise)

1) can each component of the print process by neutralised by another component; In a B&W darkroom is it really necessary to mark the trays?
to be honest I used to, but lately have had no problems just using trays and washing before/after use. Mainly this has to do with marker rubbing off, never getting around to doing it permanently. I figured that If you can pour all 3 into a Jobo then why are trays any different??
I understand to a point about pH issues with mixing different parts of process, but do the offending chemicals eat into the plastic?
or alternatively;
What chemical would neutralise
a) developer b) Stop c) fixer, d) washaid e) selenium

2) what mixing graduates need to be DEFINITELY kept separate and marked for using only with..... (I tend to use 1 graduate for all and wash thoroughly after use)

3) What chemicals will 'grow' crystals if left in trace amounts on bench, and for those specific chems, what is effective neutraliser for each?

4) when mixing powders, what are the nasties, or ones of note to keep pedantic about? I have all sorts in my cupboard, and tend to just individually tip them on a bit of paper laying on scales then bin the paper afterward. This could be developers, fixers, washaid chems, etc. I can formulate a list of specific chems if requested.

5) Sure cleanliness is important in the darkroom, but if trace amounts are sufficient to cause issues, my question is ; what are the ones that are really worth being careful with contamination wise, and is there are particular product or chemical that can be globally applied in a certain dilution to keep everything neutral and chemical free?

I have taken to using throw away paper towels for hands, and disposable gloves when scrolling, but there are still common towels or areas that will get a build up of residues, that I am convinced water does not help, as there are often blotches on the bench when I come in after a week or 2 of last session.

3-Sep-2017, 05:06
You just have to be neat, don't drip/spill anything, but if you do, wipe-up ASAP using a wet towel or sponge, and wipe dry with a clean cloth/towel...

To answer your questions;

1/A thorough wash and dry of your plastic + other trays/tanks/tongs/grads, etc is fine if you do not let chems sit in them for too long where they would start to dry inside...
The plastics are chosen that won't be attacked at your normal mixing strengths... Water is the ideal solvent for all of the common chems... Some old chems might stain if inside too long, and pyrogallic acid developers are hard to clean up after drying up... Note that many home cleaning solutions contain many of the same ingredients, are more concentrated, so nothing will kill or maim you if used carefully... Make sure nothing dries that can be raised as dust you can breathe...

2/ If everything is very clean, used once and carefully cleaned, and not used to store chems for a long time, you can mix up the vessels...

3/ Any... Even water will leave a residue... Clean & dry anything wet...

4/ No standard B/W chem is horrible... Most of the bad stuff is history... But some can cause irritation (and allergic reaction with some persons) so use gloves, eye protection while mixing, and try not to breath the fumes... Consider a vent system that keep you happy and healthy...

5/ Working or stock dilutions are OK to store... Some things that were strong were glacial acetic acid, but now not common in home labs, that were to be stored carefully...

So keep everything clean, don't let chems dry on anything, good housekeeping, keep out of reach of kids and pets, label everything well, store in a cool, dark place, use fresher chems that don't turn bad, read the instructions, dispose properly, keep the stuff off of you, and don't drink or bathe in the solutions, and you will be fine... ;-)

Steve K

3-Sep-2017, 05:33
I keep a separate tray for bleaching. Almost all bleach kits I have bought for bromoil or toning indicate to use the tray only for bleaching. I have noticed that the older Kodak yellow tray I generally use for developer has a nice silvering layer that I can't scrub off. I wash and dry at the end of each session with hot water. Mixing vessels do not seem to cross contaminate, but I suppose if one were OCD they might prefer to use dedicated vessels. Certainly in a shared darkroom you want things labeled.

Bruce Barlow
3-Sep-2017, 07:41
I just label everything with a Sharpie, and always only put that chemical in that container - including "dedicated" trays. That way, nothing ever gets into anything else.

Everything also gets washed well after each use.

Never had any kind of a problem.

Doremus Scudder
3-Sep-2017, 10:44
+1000 to what LabRat posted above.

I'll only add a couple of things:

Used fixer can be stored and taken to a local commercial photo lab for silver recovery. If you have one in your area, that is the most eco-friendly way to deal with used fix (or, alternately, you can look into home silver-recovery methods yourself.

Selenium toner can be replenished and reused. Search for my posts on this if you're interested in this.

To avoid dust when mixing bagged powders, cut a corner off the pouch and submerge this in the water of your mixing vessel when you pour the contents out. This keeps everything under the water level. Rinse the pouch when it's empty and add this to the mix; no more chemical dust.

Wear nitrile gloves when working with pyro developers and selenium toner if you develop with hands in tray; or use tongs etc. Wash hands thoroughly after spills and after the work session.



4-Sep-2017, 03:12
Thanks all, have confirmed my suspicions.... Nitrile gloves are great, have just got into using them.

So they key is water and keeping things dry it seems!