Liquid Hardware & Metal Contact
Executive summary
Wet latex and the water you leach a dipped film in are picky about metal. Brass, copper, and galvanized iron do not belong in the compound, the tank hardware, or the leach-water fittings. Copper also stains a fresh dithiocarbamate-cured deposit brown, even from the trace on skin after handling coins.
Once the film is dry, the same copper catalysis still ages the rubber. This page is metal contact on the liquid path: wet compound, leach water, and dipped or cast film. Snaps on cut sheet live in Sheet Hardware & Metal Contact. The full contact grid is the Compatibility Matrix.
Wet latex and leach water
All metal that touches the liquid must be black iron, stainless, or another metal the handbook treats as harmless to latex. Brass or copper fittings cause serious deterioration of the rubber in the latex. Galvanized fittings make coagulum.
The same metal ban applies to dipped-goods equipment and to the pipes and fittings that feed a warm-water leach tank. Do not reuse leach water unless the leached junk has been taken out.
What is a leach tank?
In coagulant dipping, a warm-water leach rinses salt out of the gelled film before the piece is dried. The handbook’s metal rules for the dip tank also apply to that rinse: no copper or brass in the fittings that bring water in.
Example: a brass hose barb on a bottle of compounding latex, or a galvanized bucket used as a rinse. Both are the contact the sources forbid.
Copper on wet or fresh film
Deposits from a dithiocarbamate-accelerated compound turn superficially brown when they see minute traces of copper. Wet deposits are the worst. The stain is copper(II) dithiocarbamate. The handbook’s remedy is to stop using that accelerator class, not to polish the mark.
That is a cast- or dip-film cure problem. It is not a snap-install trick.
Cured dipped or cast film
Trace copper still catalyzes oxidative aging after the film is dry. Industrial compounds that will see copper use 2 phr total antioxidant: one phr for oxidation, one phr held for copper. Sudsai notes dark spots from copper in containers.
What is phr?
phr is parts per hundred rubber: parts by weight of additive per 100 parts of dry rubber.
Verified clean stainless is acceptable plant metal for the liquid. Sweat in a crevice on a worn dipped film is not given a wear-time rating in these sources.
Aging morphology after the film is made: Liquid Aging, Storage and Care.
Deep dives (optional)
Deep dive: Concentrate metal limits
Industrial concentrate specs (ISO 2004 / ASTM D1076) track copper and manganese as poisons. Sudsai cites a Thai copper limit of ≤8 mg/kg on total solids. Those numbers are feedstock specs, not a snap-alloy grade.
Deep dive: Dithiocarbamate copper stain
No workaround for the brown copper(II) dithiocarbamate mark except changing accelerator class. Avoid copper contact with dithiocarbamate cures, including wet deposits.