- Film on the surface of the wine
Exposure to air and failure to add Campden tablets can allow a thin white film to cover the surface. This film wrinkles or breaks if the wine is disturbed. If not
treated, the alcohol content of the wine is reduced, off-flavours develop, and the wine becomes undrinkable. Add 2 Campden tablets per gallon and filter the wine to remove as much yeast as possible. Bottle the
wine to make sure to fill the bottles within half inch below the cork. Drink the wine within a few months as the infection may return. Wines affected by an off-flavour may be re-fermented by Refermentation Method 2. If badly affected, they should be thrown away.
- Mould on the surface of the wine.
This can be distinguished from film yeast by thicker, more solid spasms of mould which do not form a continuous cover over the surface of the wine, and which can be a
variety of colours. If mould grows on a finished wine, it indicates that fermentation was very far from complete. As some mould can produce poisons substances, infected wines must be thrown away.
- Finished wine too dark.
This may be due to the use of highly coloured must, see note on the Concentrate is too dark. However, oxidation (caused by unnecessary
syphoning) can also darken the wine. See oxidised taste.