6.3.3.c Monitoring corking

The rate of compression/insertion of the cork not being appropriate, i.e. compression should be slow and the cork should then be rapidly inserted into the bottle neck. The overall speed of the corking machine must also be monitored: if it is too fast, the corks may not be pushed in correctly. The risk is the same if the speed is too slow.

Care must also be taken to ensure that the neck is not wet, both during the filling process (by managing the filling spout pressure), and during the movement of bottles on the sorting line due to shocks or jolts, or the formation of foam that splashes out.

The bottle's neck alignment must be verified to ensure its properly centred, misalignment of the neck below the corking axis can lead to poor corking or even snagging of the neck head. The grip on the neck by the corking machine's jaws should also be checked. The integrity of the jaws must be monitored because a wrinkle in the cork created by damaged jaws can result in the bottle leaking.

Following corking, the internal bottle pressure must be verified, it should not exceed atmospheric pressure. An aphrometer can be used to measure the pressure under the cork a little while after corking (about an hour).
For conventional corking, the pressure should be the atmospheric pressure (1 bar). If corking is carried out using C02, the pressure should be slightly lower than 500 mbar. Finally, in the case of vacuum corking, the pressure should be zero or slightly below zero.

The cork should be pushed fully into the bottle's neck, but should not be pushed in too far.

Some time for the bottles to stand upright must also be taken into account. Following compression and insertion, the cork's elastic behaviour allows it to adapt to the neck's shape and ensure an effective seal. This can take anywhere from 30 seconds to a few minutes, so bottles should be allowed a minimum of three minutes of standing time before being stored horizontally. This reduces the risk of bottles leaking. This risk can be increased if the bottle neck was wet.