How are Wine Corks Made?
May 30, 2019
Ever wonder how a wine cork is made? Winemaker Paul Steinauer recently traveled to Portugal for a behind-the-scenes look into the cork-making process and the operations of Flora Springs’ cork supplier. Here’s a peek into how corks are made.
First, a cork harvester carefully strips the cork bark from the tree.
Then the cork bark dries out on pallets for several months.
After drying, the cork goes into stainless steel tanks where it is submerged in water to be rinsed, cleaned and re-hydrated.
Then, the tops and bottoms of the outer bark is removed by a stripping machine.
And the bark is cut to the proper width.
After each cork is individually punched out of the bark, it is run through a machine that measures its density, and therefore its ability to contain liquid. If it does not meet a specific density, it is discarded.
Our supplier selects cork lots from only the top-quality manufacturers, and then hauls the lots to their facility to undergo additional quality control. They test for appearance and perform a sensory analysis. The corks are warmed to enhance any odor compounds that may be present. They are looking for Trichloroanisole (TCA), which is better known as cork taint and can damage the wine—as well as any other negative odor compounds. If any negative compounds are detected, the entire lot is returned to the manufacturer.
Random samples from various lots are then placed in these small bottles to undergo a soak test. This test will detect any TCA that may not have been found during smell testing.
Once the lots have passed all quality control requirements, samples from each lot are archived at the supplier’s headquarters. If we ever discover a problem with a number of corks, the supplier can reference the problem corks with samples from the same lot to determine what issues may be present.
A great deal of work goes into the cork-making process, every cork is handled approximately ten times by the time it is approved for use. The “simple” wine cork is an expensive part of the overall wine packaging costs, but necessary to ensure the quality we expect to protect our wines.
Five Fun Facts:
- Cork trees are oak trees.
- Cork bark is harvested from 35 – 200 year old trees.
- For most 750mL closures, the bark is harvested every seven years.
- Most premium corks are harvested in Portugal; Spain is the only other significant producer.
- All of the corks Flora Springs uses are harvested in Portugal.