All about cork stoppers for bottling wine and spirits.
Corks for bottling wine and spirits can broadly be classified as:
- Wine corks:
- Natural corks: Made from solid cork without any binding material
- Composite corks:
- Agglomerated corks: normally made with top and/or bottom pieces of natural cork with small cork granules bound (glued) between the natural cork.
- Micro-agglomerated corks: Natural cork granules bound (glued) together to form a solid cork.
- Synthetic corks: Made fully from synthetic materials
- Spirit corks
- Flanged corks:
Wine: Natural Corks:
Natural corks are used for bottling still wines. The length of the cork is determined by the client preference but care must be taken with respect to fill height and head space between the closure and the wine. Each bottle has on it a measurement in mm indicating fill height from the top of the bottle. A headspace of 15mm is needed to ensure safe storage conditions. Most bottles indicate 63mm. This less 15mm gives 48mm. Therefore the maximum ideal length is 45mm considering insertion of the closure 1-2 mm into the bottle. For longer lengths there is a risk of internal pressure since this will be impacted by insufficient headspace.
The diameter of natural corks should always be 6mm larger than the bottle bore. Bottle bore specification must be obtained from the respective glass companies. In general South Africa has a specification of 17.5mm +-0.5mm. However, there are some South African made bottles that meet the European specification of 18.5mm +-0.5mm. The 17.5mm takes a 24mm. Considering the potential storage and transit issues an 18.5mm bore is recommended to take a 25mm closure.
Natural Corks are graded by porosity that is essentially aesthetic but can impact dust particles in the end product. The lower the porosity the higher the quality and cost. Different qualities of corks are available: (from highest to lowest quality)
Hand selected Flor (highest quality)
First (lowest quality)
Natural wine corks are normally available in the following sizes:
- Normal wine (750ml) bottles:
38 x 24 mm
- 45 x 24 mm
- 45 x 25 mm
- 49 x 24 mm
- 49 x 25 mm
- For large bottles (i.e. 3 - 18 Lt)
54 x 28 mm
- 54 x 30 mm
- 54 x 33 mm
- 54 x 37 mm
Wine: Agglomerated corks:
Wine: Micro-agglomerated corks:
(commercially known as Pietec corks)
These are available in the following sizes:
- 38 x 23 mm
- 38 x 23.5 mm
- 38 x 24 mm
- 44 x 23 mm
- 44 x 23.5 mm
- 44 x 24 mm
Wine Synthetic corks:
Spirits: Flanged corks:
These are normally used for port, pot distilled brandy and other spirits.
Spirits: Wooden Flange corks (also called bartop corks)
Wooden Flange Corks are available in the following sizes and qualities:
- 27 x 19.6 mm Super / Extra
- 27 x 20.2 mm Super / Extra
- 27 x 20 mm Super / Extra
- 30 x 20 mm Extra
Spirits: Black Flange corks (Black bartop corks)
Black Flange Corks are available in the following sizes and qualities:
- 27 x 19.6 mm Super
- 27 x 21.2 mm Super
- 27 x 20.2 mm Super
- 30 x 18 mm Super / Extra
Corks should not just be inserted into a bottle and be expected to provide a closure that works "foolproof". A few practises should be noted:
1. For wine bottling: (will be added end of March 2012)
2. For spirit bottling: (will be added end of March 2012)
Cork taint and how to remove it:
This is an extract from a wikipedia article. The full article is available from this link.
Cork taint is a broad term referring to a wine fault characterized by a set of undesirable smells or tastes found in a bottle of wine, especially spoilage that can only be detected after bottling, aging and opening.
Though modern studies have shown that other factors can also be responsible for taint – including wooden barrels, storage conditions and the transport of corks and wine – the cork stopper is normally considered to be responsible, and a wine found to be tainted on opening is said to be "corked" or "corky". Cork taint can affect wines irrespective of price and quality level.
The chief cause of cork taint is the presence of 2,4,6-trichloroanisole (generally called TCA), and/or 2,4,6-tribromoanisole (generally called TBA), in the wine, which in many cases will have been transferred from the cork, but which also can have been transferred through the cork rather than from it.
Corked wine containing TCA has a characteristic odor, variously described as resembling a moldy newspaper, wet dog, damp cloth, cardboard or damp basement.
In almost all cases of corked wine the wine's native aromas are reduced significantly, and a very tainted wine is quite unpalatable, although harmless.
While the human threshold for detecting TCA is measured in the single-digit parts per trillion, this can vary by several orders of magnitude depending on an individual's sensitivity. Detection is also complicated by the olfactory system's particularly quick habituation to TCA, making the smell less obvious on each subsequent sniff.
Filtration and purification systems now exist that attempt to remove the TCA from corked wine to make it drinkable again, though there are few means of reducing the level of TCA in tainted wine that are approved by the TTB (formerly BATF).
One method of removing TCA from tainted wine is to soak polyethylene (a plastic used for applications such as milk containers and plastic food wrap) in the affected wine. The non-polar TCA molecule has a high affinity for the polyethylene molecule, thereby removing the taint from the wine. The surface area of polyethylene needed to reduce the taint to sub-threshold levels is based on the TCA level in the affected wine, temperature, and the alcohol level of the wine.
This can be done at home, as advocated by Andrew Waterhouse, professor of wine chemistry at University of California, Davis, by pouring the wine into a bowl with a sheet of polyethylene plastic wrap. For ease of pouring, a pitcher, measuring cup, or decanter can be used instead. Effective within a few minutes, the 2,4,6-trichloroanisole molecule is chemically similar to polyethylene and will stick to the plastic.