How Wine Corks Affect Aging Wine
A cork is designed to keep wine in a bottle–but the idea of the cork, the associated pop, and the terrible cork-crafts that litter wine merchants’ shelves are proof that cork and wine are more than cozy. With the availability of new materials, and the known benefits of some alternative closures, there are many growing cases against the use of cork. I’ll break down some of the cork related issues and show how wine corks affect aging wine. Maybe I’ll even convince you to stop making coasters, trivets and corkboards for your friends.
Where do corks come from?
Cork bottle stoppers are made from the bark of cork oaks. The tree is not cut down and only up to half of the bark is removed at any one time. This is a highly skilled, labor intensive process with special tools and complicated logistics. Imagine peeling the delicate bark off of a massive tree, cutting it into uniform sheets and transporting it to the processing plant without breaking it. These are reasons why cork closures are more expensive, and why there is some pressure to move to alternative closures.
Plastic is forever and aluminum takes a ton of energy to make. Cork is by no means a perfect product, but it has stood up very well to synthetic closures in terms of sustainability and environmental impact. 50% of northern Portugal’s economy is based on cork and they have taken a huge hit from the use of synthetic corks and aluminum caps. Centuries old cork forests have been cut down to make room for new industries, which is endangering certain animals and setting the production of cork back decades. Cork trees need to be 25-30 years old before their bark can be harvested.
Know Your Corks:
100% Natural Cork Stoppers
This is what you think of when I say cork. It’s one piece, comes in grades (based on surface, water content, porosity, and visual inspection) and is the best choice in most cases. This is the only cork stopper you should trust for aging wine much beyond 5 years or so, because its spongy flexibility keeps its seal viable the longest.
Take the cork from above and fill its pores with glue and cork dust. These corks look smoother, glide out of the bottle when you pull them, and are still good for medium aging.
Two or more large cork pieces glued together. These are denser than single piece corks, and are a way the cork manufacturers can use up their scraps. These are also the only way to make giant corks for giant bottles (remember, corks come from a sheet of bark, so there is an inherent size limit). They should also not be trusted for prolonged aging.
The particle board of corks; basically these are a plug made of cork dust and glue. Cheaper, pretty dense, and not to be trusted to seal your wine beyond 1 year or so.
I call these liar corks! They are agglomerated corks with full cork discs on either end. There are reasons to do this: like with sparkling wine where they want a larger cork diameter to contain the pressure. It is also a way to ensure your cork is uniformly dense throughout while improving the seal made by simple agglomerated corks. It still feels like a sneaky way to make the cork look solid from the outside of the bottle though.
DIY Cork Crafts
These are promoted as a way to recycle corks. I’d just like to point out 100% natural corks will biodegrade, which might be a less ugly proposition. Good for you, though! cork board sourced from misskoco on flickr
Look for our upcoming feature on alternative and synthetic closures to get your bottle stopper knowledge to professor level.