Winemaking is an age-old craft so it’s no surprise that there is a lot of misinformation and lore surrounding it. This can be entertaining and even amusing at times but it can also cause problems for novice winemakers looking for advice.
Sealing wine bottles with cork is one area where this is apparent. One of the most persistent fallacies is that you should boil wine corks before using them. Don’t do it. This will damage the cork structurally and could result in spoiled wine. Most wine corks today are surface treated for easier insertion and should be inserted dry. A floor standing corker is the easiest way to do this.
Here is a list of corking guidelines recommended by the Portugal cork industry. Some of this information is intended for commercial bottling but there’s lots here for the craft winemaker too.
- Use corks with a surface treatment for a better insertion into the bottle. Never boil, or soak in wine or water before using.
- If you cannot use all the corks from a bag at once, close the bag promptly and use the corks quickly.
- Corks must be stored in a clean, well ventilated place, free of volatile and aromatic products that may contaminate them, at a temperature of 15 to 20°C and at a relative humidity of 50-70%.
- Use corkers with slow compression and fast insertion rates. A cork must be inserted as rapidly as possible to avoid creating any creases at the lower end.
- Compression should not exceed 15.5 mm for a 24 mm diameter cork.
- Before laying bottles on their side, they must be kept in an upright position for a period of time that varies according to the humidity of the storage area and compression rate of the cork.
- Leave a “head space” of at least 15 mm between the cork and the wine. This guarantees an appropriate head space to compensate for temperature variations that should not exceed 10 Celsius.
- Ensure the compression of the jaws of the corker are set to the right diameter and are properly maintained.
- The injection of carbon dioxide or the use of vacuum during bottling will reduce internal pressure near to zero and minimize the risk of wine leakage.
- Do pasteurization before and not after bottling.
- Prepare your stock of corks well in advance of utilization (6 months). Do not rush preparation close to the time of bottling.
- Bottle in a clean, well ventilated area.
- Keep wine cellars free of insects using atmospheric electrocution. Some insects will lay eggs on the corks whenever a little wine extract exists. This causes worm development in the channels between the cork and the bottle neck.
- Avoid a wet neck during corking. Should this happen, the cork will expand over a film of liquid and could cause the formation of creases and microbiological growth on the extract of dry wine.
- If using a capsule on top of the cork, avoid creating a vacuum space between cork and capsule.
- Only buy corks from a supplier that can give you a guarantee of the hygienic history of their production.