A cork is a cork, of course, of course. Or is it?


We hear plenty in the mainstream media debating the merits, or lack thereof, of alternative closures and packaging like screw caps or boxes. But I’d like to draw your attention to the different types of corks that you may find yourself pulling out of a bottle. Learning to identify the type of cork in the bottle will provide you with information about the wine producers and maybe even the wine itself. Not all corks are created equal.

The above image depicts, from left to right, a 100% natural cork, an agglomerate cork, a 1+1 cork, and a synthetic cork. Let’s discuss them in the order of highest-to-lowest cost, quality, and performance.

Natural Corks

The oldest cork is also the most coveted. The 100% natural cork is the bark harvested from cork oak trees, which is gently and sustainably stripped by hand. Corks are punched out of these strips of wood, similar to the way a three-hole puncher works on a piece of paper. The best cork for wines with a longer shelf-life–wines that benefit from aging–come in various quality grades. While different cork manufacturers have their own rating scale, natural corks are graded based solely on their visual attractiveness. The higher percentage of visual flaws, the lower the grade. Often, cork suppliers will perform more strict cork taint screening for their higher grades.

Different types of finishing washes may or may not give a tint of color to the cork. Cork, being a natural product, will have some color variation. Some wineries prefer uniformly white cork because they feel it implies a higher quality. This is not necessarily the case. A very white looking cork was probably bleached to mask the natural, aesthetic imperfections that wouldn’t impact the wine anyway. There is one cork manufacturer that even offers a proprietary wash that gives the cork a pinkish hue.

1+1 Corks (aka Technical Corks)

These corks are made up of an agglomerated shaft, which look similar to and feel like natural cork. When the cork bark is harvested, after the closures are punched for the natural corks, a hole-y sheet of scrap bark remains. It’s sort of like when you’re making cookies: the dough is rolled out flat and a cookie cutter removes whole circles, and you’re left over with a perforated scrap dough. That scrap bark is processed in a way where it is ground into small, uniformly sized particles. Those particles are cleaned, treated, and glued together. Thin discs of 100% natural cork are glued to either end of the micro-agglomerated shaft. Because of the discs, only natural cork comes into contact with the wine, but these corks are more cost effective than 100% natural cork. These closures are best for wines with a shelf life of roughly five years or less.

Agglomerate Corks

Cork manufactures all have different proprietary names for these corks that are the same as the 1+1s, but without the natural cork discs on either end. These are cheaper corks and you should only find them on wines that are intended to be consumed young (2-3 years shelf life). Agglomerate corks may have a higher incidence of cork taint (the higher surface-area to volume ratio of natural cork, due to grinding into small particles, makes it more susceptible to contamination at certain points in the process). In this instance, the agglomerate is in direct contact with the wine (versus the 1+1). It would be a red herring to discover this cork in anything other than an inexpensive bottle of wine, or in one where the winery recommends aging. Those claims, with a cork of this quality-level, would reek of dishonesty and disingenuous sales.

Synthetic Corks

Made from plastic compounds,synthetic corks are impossible to miss especially when they come in a variety of gaudy colors. Although, buyers beware, sometimes the plastic cork may be decorated in such a way to resemble the appearance of natural cork. Squeeze it, the synthetic corks tend to be more rigid and have less give. Smell it, there will be no hints of vanilla or oak, but rather it will smell of the plastic that it is. Extracted using a corkscrew, these corks are cheap and terrible (although improving). While they eliminate the chances of having a “corked” bottle, they do not provide a very good seal and are only acceptable for wines meant to be consumed immediately (18 months or less). A synthetic cork is a sign of a mass produced, lesser quality, inexpensively manufactured bottle of wine.

Now that you know how to identify the different types of cork closures, you understand more about the overall quality of the product. Some wineries, like in any business, may try to cut corners to increase their profit margin. But, by and large, each of the aforementioned closures have their place in the market, and on your dinner table. Just know what you’re paying for.

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