The cork using specification

The following is from a cork manufacturer.

Important Information for Natural Cork Use

1. Store corks at ~70 F for at least 24 hours before use. 

2. Bottles should be left upright at ~70 F for a minimum of 2 hours after corking. 

3. Fill level. There should be 15 mm of headspace between the bottom of the cork and the wine.

4. Do not moisten (soak) or heat these corks before use. They have surface treatment for easy corking and soaking removes the coating.

5. Bottling temperature should not exceed 60° C. 

6. Internal bottle neck diameter should be minimum of 6 mm less than cork diameter for still wine, 7 mm for sparkling wine/beer/cider up to 1.5 bar pressure.

A cork is compressed a great deal during corking. For example, a 24 mm diameter cork is compressed to 16 mm (and then expands to 18 mm, the diameter of the opening in the bottle). The bottle is sealed tightly as the cork relaxes from this compression. The relaxation does not happen instantly---it typically takes about 3 hours to reach 95% expansion and up to 24 hours for full expansion in the neck of the bottle. If the cork is cold, the cork loses its elasticity and will not relax properly. If you lay a bottle down before the cork has fully expanded, wine can fill the space between the cork and the bottle, causing a poor seal including possibly leakage. 

For spirits, cork should be ~1 mm larger than inside diameter of bottle.