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Updated October 2026

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What this covers Spent fixer carries silver And there is no leaching procedure to run The determination happens before you dilute Which closes the obvious escape The product side is about air, not light And one leaf is not a chemical at all References

The hard container here is the one you fill at the end, not the one you buy the chemistry in.

What this covers

Darkroom chemistry, decanted developer, fixer storage and film canisters. Four leaves, and the regulation reaches one of them in a way it reaches nothing else in this library.

Spent fixer carries silver

Which is a toxicity characteristic contaminant. If the concentration in the waste is at or above 5.0 mg/L it exhibits the characteristic and carries EPA hazardous waste number D011. Spent fixer from ordinary use commonly runs well above that.

And there is no leaching procedure to run

The rule says that where the waste contains less than 0.5 percent filterable solids, the waste itself, after filtering, is considered to be the extract. Fixer is a liquid, so you compare the silver in the liquid directly against 5.0 mg/L.

The determination happens before you dilute

At the point of waste generation, before any dilution, mixing or other alteration occurs. So pouring spent fixer into rinse water and measuring the result is not a determination, it is the thing the clause forbids.

Which closes the obvious escape

And it is the single most useful sentence on this page, because diluting to get under a number is exactly the first idea anybody has. The obligation attaches to the waste as generated.

The product side is about air, not light

Developer oxidizes on contact with oxygen. A part-full bottle of stock developer goes off while a full one keeps, which inverts the usual packaging instinct: several small bottles filled to the top rather than one large one slowly emptying.

And one leaf is not a chemical at all

A film canister is a light-tight container for rolled film, which is a different article from anything on this shelf. Nothing here is light-tight in that sense and a plastic bottle is not a film can.

References

40 CFR 261.24, the Toxicity characteristic. A solid waste exhibits it where the Toxicity Characteristic Leaching Procedure extract contains a Table 1 contaminant at or above the listed level, and where the waste contains less than 0.5 percent filterable solids the waste itself is considered to be the extract. Table 1 lists D011 Silver at 5.0 mg/L. law.cornell.edu

40 CFR 262.11, Hazardous waste determination and recordkeeping. The determination must be made at the point of waste generation, before any dilution, mixing or other alteration occurs, and again if the properties change; and it may be made using knowledge of the waste including its origin, composition, the process producing it and the feedstock. law.cornell.edu

Written from federal regulation and from measured catalog data, not from a darkroom. Hazardous waste regulation is federal with authorized state programs on top, and many states and municipalities regulate silver discharge to sewer separately. The determination for a specific waste is the generator’s to make.