During and after bottling, but prior to consumption, wine can be subjected to a range of different circumstances, such as:

• Aeration, for example at bottling
• Light, for example on shop window displays
• Low or high temperatures
• Time

It is important that the wine is reasonably stable so that it can resist these effects with as little change as possible. This stability can never be guaranteed under all circumstances; the winemaker must predict the conditions that the wine will endure prior to being consumed, and then use stability tests to see if the wine will remain stable under these conditions. Any wine failing a stability test must be treated appropriately prior to bottling. If these precautions are not taken, the wine may alter or throw a deposit in the bottle, which would lead to all the wine being recalled and either destroyed or treated and re-bottled, which is a very expensive operation.

The three main instability problems in wine are linked to oxidation, chemical instability and microbial spoilage.