Correctly preparing corks for bottling wine is important. Not only should the wine corks be sanitary, but they should be softened just enough to allow your corker to put them in the wine bottle with ease.
There are two basic ways to go about sterilizing and softening wine corks: This first involves submerging the corks in a solution of sodium metabisulfite and cold water. The second, involves steaming the corks in water.
Cold Soaking The Wine Corks:
Sodium metabisulfite and cold water makes a solution that will sanitize the corks. This solution can also soften the corks if they are allowed to soak long enough, usually over night, and it's very simple to do.
Mix 1/8 teaspoon of sodium metabisulfite to each pint of water and submerge the wine corks in the solution. Corks like to float. So I have found that using a container with a lid of some type will help you to get this accomplished. Use the lid to push down the corks into the solution.
Let the wine corks soak long enough to make them slightly soft. You do not want the them to be spongy. You want them to be firm, but still give just a little. Remove the wine corks from the sanitizing solution and allow them to drain for a few minutes in a colander, strainer or something similar.
Steaming The Wine Corks:
Preparing corks for bottling by steaming them is much quicker than just soaking them, but it does take some care. It is very easy to over-steam the wine corks making them very spongy and hard to press into the wine bottle without mangling them.
Also, too much heat on the wine corks for too long will cause them to become brittle and crumble later on when they are pulled from the wine bottle. Excessive heat denatures the wine cork causing it to deteriorate while in the bottle.
Bring a pot of water to a boil then turn the burner off. Put the corks on the steaming water and place a lid over them. In just a matter of 2 or 3 minutes the corks should show some signs of softening. Once you feel the corks firmness start to give – just a little – rinse them in cold water to cool them down. They are then ready to be used.
Which method you use for preparing corks for bottling is up to you. I feel the preferred method is to cold soak them, but if you forget to start that the day before bottling the wine, I can understand you wanting to steam the wine corks instead.
Ed Kraus is a 3rd generation home brewer/winemaker and has been an owner of E. C. Kraus since 1999. He has been helping individuals make better wine and beer for over 25 years.