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Comment by codpiece | Hacker News Reader

I would like to do more of this, I have camera and processing equipment, but it's extremely hard to dispose of the chemistry. Some of the ingredients are highly toxic to fish.

Lots of discussions on waste disposal on forums, but unless your town recycles chemistry or you have a college with a film lab nearby, your (my) options are limited.

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Pour the used chemistry into cat litter and let it dry out, then dispose of the litter in a plastic trash bag.

Is this recommended? It sounds like a much better alternative than “it’s not too much silver halide down the drain”

It's recommended by me, at least.

I haven't tried it myself, but caffenol[1] might be an alternative if you're shooting B&W.

[1]: https://en.wikipedia.org/wiki/Caffenol

The environmental risk is from unexposed silver halide that you rinse off the film in the fixing step. The developer isn't really the harmful chemical; though do read the MSDS for the developer you use and follow its instructions. (I wouldn't want to absorb it through my skin, breathe too much of the vapor, drink it, etc. True of the chemicals I use to clean my bathroom, too. Risk can be mitigated through proper safety measures!)

People reuse fixer, or at least I do, but there is a point where it's exhausted and needs to be discarded. My understanding is that the environmental risk from hobbyist developing is exceedingly low and dispose of it accordingly. If I were deeply concerned, I'd just let the liquid evaporate and store the solids in a plastic bag in a drawer. (That seems to be the NileRed approach to metal waste. When you're tired of the bag, you pay for professional service to take it away.)

if fix is supposed to keep the paper from discoloring over time, which is not immediately aparent, how do you know when your fix needs to be replaced?

I am not sure about discoloration -- I don't develop paper very often, and I don't use fixer for any reason other than to remove unexposed silver halide. (Without a fixing step, you could expose the film to light and run it through the developer again, and have another image. Or most likely, just completely ruin the negative. Fixers claim to do a lot of things, but washing away silver halide is the reason it's a mandatory step.)

For measuring exhaustion, I look at the datasheet to estimate the area of film that it can fix before exhaustion, and keep track with tick marks on my bottle. I typically use Ilford Rapid Fixer diluted 1+9 (100mL fixer -> 1L of working solution). 5L of fixer develops 2000 8x10 sheets, so 100mL does 40 sheets. I mostly shoot 4x5, so that's 160 sheets. When there are 160 tick marks on the bottle, I discard it and make a new batch. (Honestly, expiration dates are really my limiting factor. 6 months in a tightly capped bottle.)

Film photography is 99.9% bookkeeping and 0.1% art ;)

I have recently been using my room as a pinhole camera. I have wasted so much paper and money to also come to that conclusion. Next on my to buy list is that Ilford darkroom paper light meter. But it's hard to take notes in the dark.

I have been dropping steel wool into the developer and letting it sit for a day or so. I had read about this in a few forums — I assume the iron reacts in some way with the developer to create a chemical less toxic.

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