Cork'd or Uncork'd?

As an addendum to Gary's post about bottle shapes, this post explores cork varieties.

First, a threshold matter - why do corks matter? According to Winederlusting, cork type affects the flavor of wine and protects the wine as it ages.

Now for the four (five including screw tops) most common cork types:

1. Natural Corks: "Natural" is a catch-all term for corks that are made from cork tree bark. Within the natural category are three subcategories:

• One-piece: cut from one sheet of cork bark. One-piece corks are best for wines meant for long-term aging, because they have fewer holes and thus let in less air. They also naturally expand and retain structural integrity over long periods of time.
• Multi-piece: at least two pieces of cork (usually scraps) are glued together. Because multi-piece corks have poor structural integrity, they're ill-suited for wines that need extensive aging. 
• Colmated: tiny holes within the natural cork are filled in with cork dust and glue. Colmated corks fall between one-piece and multi-piece in terms of structural integrity. The general rule of thumb is that colmated corks should be used for wines that will be aged less than three years.

2. Agglomerated Corks: Made of a combination of natural and synthetic (see next) materials, agglomerated corks are hybrids. Agglomerated corks tend to be cheaper than their natural counterparts. Because they let more air into the bottle than one-piece natural corks, they're best for wines that will be consumed within a year of bottling.

3. Double Disk: Also known as agglomerated "twin top" corks, double disk corks feature two natural cork disks at both ends, while the middle "meat" is agglomerated. As one might expect, these corks are best for medium-aged wines (i.e., they let in less air than agglomerated corks, but more than the natural varieties). 

4. Synthetic: While cork producers are experimenting with various synthetic materials, synthetic corks are most commonly made from an oil-based plastic or corn and sugar cane polymers. Because synthetic corks can be made more or less dense, they afford a great deal of flexibility. That is, a producer can request an exact density that corresponds with the desired level of oxygen transfer. The downside is the risk that the synthetic material leaves a chemical color and / or flavor.

5. Twist-off: Most commonly found in New World wines, twist-offs are usually less expensive than any of the four cork options. They also remove the risk of cork taint and cork degradation over time.

And that's it! I'll leave you with a cork-related fun fact: Portugal produces 50% of all wine corks, followed by Spain at 30%.