Diatomaceous earth
DE, kieselguhr, filter aid
A filter aid, rather than a fining, for wines too cloudy to filter.
Typical dose
As a filter pre-coat and body feed per the equipment, not added to remain in the wine.
When to add it
During filtration of a hazy wine.
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
Fossil-silica powder that builds a porous cake on a filter so a cloudy wine can be pushed through without blinding the medium at once. It is a processing aid that is filtered away, not something left in the wine, and the dry dust should not be inhaled.
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.
Activated carbon
A blunt last resort that strips colour and off-odours together.
Plant protein fining
A vegan substitute for gelatin and isinglass.