Activated carbon
activated charcoal, decolorising carbon
A blunt last resort that strips colour and off-odours together.
Typical dose
Bench-trial and use the least that works, roughly 0.1 to 1 g/L.
When to add it
On a wine with a colour or odour fault no gentler tool will fix.
Legal limit
No specific limit that this reference states. Additions are still governed by the treating-materials rules where you make wine, so check them.
Vegan
Yes. Nothing animal-derived, so a wine fined with it can still be labelled vegan.
In practice
Adsorbs almost everything, which is both its use and its danger: it will pull pinking, browning or a light taint out of a white, and the wine's own aroma and colour with them. It is a tool for rescuing a fault, never for routine polishing, and every use is trialled to the minimum.
Others in fining and clarification
Bentonite
Adsorbs unstable protein to prevent haze in whites and roses.
Isinglass
Fish-derived collagen that polishes whites to brilliance at a tiny dose.
Gelatin
Collagen that strips harsh tannin and astringency from reds.
Egg white
The traditional, gentle softener of barrel-aged red tannin.
Casein
Treats browning and light oxidation or taint in whites.
PVPP
A synthetic that removes browning, pinking and bitter phenols.
Kieselsol
A negatively charged fining, paired with gelatin for a compact lees.
Sparkolloid
A polysaccharide clarifier for stubborn hazes that resist other finings.
Plant protein fining
A vegan substitute for gelatin and isinglass.
Diatomaceous earth
A filter aid, rather than a fining, for wines too cloudy to filter.