Once in a while you come across some information that is so good, rather than extracting parts it is best just to present the whole article. Please find below a copy of an article by Tim Vandergrift on Corks and Corking. Tim is Technical Services Manager for Winexpert, makers of our Selection, Vintners Reserve, Island Mist, Chai Maison and Barons kits. In 2003, Tim was awarded the prestigious Wine Maker of the Year Award.

Bottling and Corking Your Wine

Traditional corks are made from the bark of the cork oak, Quercus Suber, which is harvested once every 20 years without endangering the trees’ life. Today, however, there is a wider range of cork choices for the home winemaker than ever before:

Agglomerated corks are made from chipped cork pieces ground to a specific size and glued together with non-reactive polyurethane glue. Inexpensive and easy to handle, these are suitable for wines that will be held for three to six months. (note Creative Connoisseur does not carry this cork as we believe they are an inferior cork)

Die-cut natural cut corks are simply punched out from cork bark. They rely on the density and elasticity of the natural cork bark to seal the bottle. Depending on the quality of the cork, you can expect your wine to last from 3 years to more than 10.

Nomacork synthetic corks are made from food-grade, super high density, foamed polyethylene plastic. They are easy to insert and extract, do not chip, split, leak or rot, and are suitable for at least 5 years of ageing, and in good cellaring conditions, over ten.

How long should your cork be? Which cork is right for you? Look realistically at how long you expect to store your wine before drinking, and figure out how much cork fits in your budget. A good rule of thumb is 'You get what you pay for.' The cheapest cork isn't always the best deal, and if you do decide to keep some bottles for the future, you may find yourself having to re-cork them in a few years.

In addition, there is the problem of trichloranisole contamination. All natural corks, both agglomerated and die-cut, contain a bad-smelling substance called trichloranisole. Industry statistics show that as much as 5% of all wine is spoiled by contact with contaminated corks—that is to say that even the costliest natural corks can spoil wine. This is why Winexpert fully endorses Nomacork synthetics.

Preparing Your Corks

If you are use a small, hand-held corker (single or double-lever types) with natural corks you may need to prepare your corks by soaking them in warm water for 20 minutes. (Note Creative Connoisseur recommends using a sulphite solution to sterilize your corks) If you have trouble getting corks to pass through your hand-held corker, you may want to try adding 70 ml (¼ cup) of glycerine to every four litres (one gallon) of warm water that you use for soaking. This ensures that the corks get enough moisture to lubricate their passage through the corker. However, this may cause them to crumble in the long term. It’s a much better idea to purchase or rent a floor corker and dry-insert high quality corks.

Nomacorks never require any soaking or sanitizng. Insert them dry right from the bag.

Some books talk about boiling and long soaking in sulphite solutions, but these are very bad ideas. Cork is tree bark, and boiling destroys it. Long soaking does the same thing. Corks can soak up sulphite solutions and transfer them to the wine. Once you have opened a bag of corks, you may need to take special care of the unused corks.

The trouble with handling very dry corks is that it’s tough to judge how long you can soak them before they become mushy. However, there is a nifty technique that you can take advantage of, if you your corks are brittle either from age or low-humidity storage. You can construct a ‘cork humidor’.

You will need a sanitized plastic bucket and lid, an empty wine bottle, and a 1.25-% solution of metabisulphite, fifty grams(eight teaspoons) of metabisulphite) dissolved in four litres (one gallon) of cool water. Fill the wine bottle halfway with the solution, and carefully stand it up in the bottom of the bucket. Gently pour your corks into the bucket, filling the space around the bottle, and put the lid on tightly. Leave the bucket in a room-temperature area for about a week. In that time the liquid evaporating from the wine bottle will raise the humidity in the bucket to about 70%, in turn raising the humidity in the corks to 6% or so, making them pliant enough for easy insertion. The sulphur dioxide gas coming off the liquid will prevent the growth of moulds or spoilage organisms, keeping the corks sanitary. No further treatment of the corks will be necessary before bottling. 

If you want to store your corks this way, replace the solution in the bottle every four weeks, and keep the lid tightly sealed. That way your corks will always be ready for use.

Corkers

There are several types of corkers available. We highly recommend a floor corker with jaws that compress the cork in an irising motion. Other corkers (twin lever, single lever, and compression corkers) rely on human muscles to compress the cork and push it into the bottles. Floor corkers, while more expensive, use levers and mechanical advantage to carefully compress the corks and insert them precisely into the bottles. They also hold the bottles steady in a spring-loaded base. They are really worth the extra money.

Loose Ends

After the corks have been inserted into the bottles it's a good idea to dry the top of the cork off with a clean cloth. This will prevent any moisture from forming mould there. While a spot of mould on the top of the cork wouldn't hurt your wine, it does look unpleasant.

After all of your bottles have been safely filled and corked, you can choose to put capsules over the neck of the bottle. While not necessary to preserve the wine, they give a nice finished look to your bottles, and when co-ordinated with labels give your wine a very professional look. Capsules are often called shrink-caps, because heat is used to shrink the plastic onto the bottle neck, holding it tightly and smoothing out any wrinkles or seams in the plastic.

The best way to apply this heat is with the steam from a kettle. At a rolling boil the kettle will produce enough steam out of the end of the spout to shrink a capsule in only two or three seconds. Be careful not to burn your fingers!

While you can use blow dryers, they are very slow. Hot air paint-strippers work better, but they aren't as fast as a kettle, and are a bit more dangerous to use. In a pinch the heat from an electric stove element will also serve to shrink the capsules on, but again, be careful with a hot stove.

You should leave your wine bottles standing upright for at least the first 24 hours after corking. The compressed air inside the bottle has to work its way out past the cork, and it can only do that if the bottle is standing up. If you immediately turn the bottle on its side, the pressure will still be there, but the wine will now be pushing against the cork, and could force it out of the bottle. After 24 hours (or two or three days: it isn't critical) you should turn the bottles on their side for long term storage.

How long will your wine keep? This is a tough question to answer as it depends on so many factors. As long as you keep it safely in a cool (60°F or lower), dark room, with good care and attention to your bottling practices, your wine will last as long as the raw materials it was made from. Better quality ingredients usually mean a wine that will age longer.