Corks are basically wood fiber that could damage some of the economy corkers which are available for home winemaking purposes if not preped properly. Before using corks, they need to be sanitized and made more pliable by one of two means so that they can be compressed more easily.
For composite cork, a 30 minutes soak in a sodium metabisulfite solution is all that is needed. For natural corks, soak for a maximum of 12 hours.
The solution can be made by dissolving 4 campden tablets in a PINT of water.
Place the corks in an empty ZIP-LOCK bag, pour the solution into the partially zipped bag. Press all of the air out and zip it closed. Leave in the sanitizing solution according to the times indicated above.
2. The second means of sanitizing is not desirable even though it is easier. Boiling the corks. Boiling will do an effective job of sanitizing but it will cause the corks to be brittle and increase the likelihood that the corks will break off in the bottle.
Once the wine is bottled & corked. Leave them in an up-right position for a minimum of two weeks. During this time, the pressure in the bottle may push the corks up. Check the bottles periodically during this time frame, using thumb pressure to push any raised corks back to the desired rim level.
After the two weeks has elapsed, the corks should be sufficiently seated to the glass that the bottles can placed in a winerack or other means to achieve a more horizontal position. From this point on, it is desirable to maintain some cork contact with the wine to prevent the corks from drying out. A dry cork will eventually allow the wine to oxidize.