A proportion of coloured phenolics in red wines are in a colloidal state, and these should be removed before bottling, as they will form a premature deposit at the bottom of the bottle with time. During the ageing process, the dissolved phenolics in the wine will gradually join together to form colloidal suspensions and then precipitate, but this is a relatively slow process and the customer will accept a phenolic deposit in a red wine which is mature.

The standard method for testing for phenolic stability is to keep clear wine at 0 - 4°C for 12 hours. The appearance of a haze indicates risk.

If a risk of precipitation appears the wine should be fined with:

• Albumin (egg whites)
• Gelatin