Wooden Corks will provide the best seal if they are allowed to remain wet and if they are in turn sealed with wax over the top to prevent air flow interaction. Synthetic seals are good but unproven over time. Alcohol will dissolve rubber, the exact consequences are unknown.
Everything ages in a barrel. Air flows between the fibers of the wood and the whisky causing aging. The real factor is the age of the wood and how long it has been used previously. JD barrels are used extensively to age rums to fantastic result, keep using them if you like the flavour and aroma they impart.
Last edited by michael; 05-04-2010 at 10:44 PM.