Instability, which is initially manifested as a white haze (white wines) and later as a reddish-brow precipitate, could result from storage of bottled wine containing levels of copper above 0.5 mg/L. Excessive levels of copper are toxic. Excessive levels of Copper in wine may be removed or reduced by treatment with a range of fining agents.
Grapes accumulate normally only a small amount of copper by natural translocation from roots. Unless exposed to significant airborne pollution or vineyard sprays, increased concentrations in wine result from contamination during post fermentation processing.