Does cork absorb water? No, cork doesn’t absorb water. It is a common misconception that has no truth to it. Cork is a buoyant material that does not have pores and remains buoyant for years. It is most commonly used as a wine stopper for years which is proof of its nature. Did you know that the ancient Romans and Greeks used a combination of cork and natural resin to plug amphorae soaked in wine and oil? Cork is a natural material that has been used by humankind for over 5,000 years. Today, about 70% of all cork produced globally is used to make wine stoppers. So, if cork does not absorb water, what is the purpose of its production? Do you want to learn about where cork comes from and what it is commonly used for? We have all the answers you seek.
What is Cork?
The cork is a waterproof floating material; the phellem coat of the bark tissue is harvested from the cork oak tree (Quercus suber) for commercial purposes. Interestingly enough, the extraction of cork neither harms the tree nor interferes with its normal growth. Therefore, cork is an organic material; it is 100% natural, including cork oak bark. However, it is occupied by 90% air, which provides it a low density and lightweight. Cork cells show a characteristic cellular structure with a typical pentagonal or hexagonal shape.
Does Cork absorb water?
No, cork does not absorb water. Cork is also resistant to mold, so water, humidity, or even high humidity is not a problem with cork bricks. Cork’s cell wall is composed of a lignin-rich central lamella (inner primary wall), a thick secondary wall made up of alternating sheets of suberin and wax, and a thin third wall containing polysaccharides. Suberin is a natural substance that lends the cork a waxy barrier. It consists of neatly arranged dead rectangular cells. These cells are impermeable due to the deposition of suberin in the cell wall. Cork prevents water loss due to evaporation. It also protects the interior against harmful microbial invasion, mechanical damage, and temperature extremes. Cork is slightly compressible, non-reactive, and sufficiently fire resistant. It is used as a bottle stopper, shock absorber, and insulator. Because cork doesn’t absorb water and can float for many years, it is also used in buoys, life jackets, and other flotation devices. A solid block of cork soaked in water for 48 hours will have 3% more mass due to water absorption. One cubic inch of solid wood or unglazed clay brick will increase many times this weight percentage of water if soaked for 48 hours.
Properties of Cork
Following are the properties of cork for which it is used most widely as stoppers:
Waterproofing
Cutin, suberin, and wax, which are present on the cork’s cell wall, make it virtually impermeable to liquids and gases. Hexagonal holes in the air-filled wall prevent access to other compounds.
Acoustic insulation and low sound transmission
With its low density and high porosity, most of the waves in the sound-absorbing material are converted into heat energy. Cork is an acoustic compensator that absorbs more than 60% of the sound affecting the surface. The high gas content cell size and low adsorption capacity make it a characteristic.
Compressibility, elasticity, and flexibility
Due to the high air content of the cells, it can be compressed in almost half without losing its flexibility, restoring its shape and size when compression is stopped. When one is compressed, the other is the only solid that has not increased. Lignin and cell wall polysaccharides give lignin stiffness and improve resistance over time.
Natural, recyclable, and renewable
Cork is a plant material that is extracted without damaging the tree and regenerated over many years. It enables a sustainable balance between agroforestry management and human behavior. Depending on the current trends in natural materials and sustainable construction, it is a typical example of a circular economy.
Miscellaneous
The suction effect by the surface of the cell is a very important characteristic when using cork as a cladding material makes it high resistance to movement and high coefficient of friction. It gets hydrated to the environmental conditions that make it hygroscopic. Moreover, it has a cushiony capacity as it is given by deformation by bending cell walls. It is an important asset for some applications, such as hats or shoe soles.
Using Cork as wine stoppers
Now that we have learned that corks do not absorb water, you must also learn about the purpose of their production. Wine corks are stoppers used to seal wine bottles. Synthetic materials can also be used for it, but they are generally made of cork (cork oak skin). Common alternatives to wine stoppers include screw caps and glass stoppers. 68% of the total cork is produced for wine bottle stoppers. Cork is produced not only in sparkling wine but also in sparkling wine. The latter is forced to mushroom the cork on the bottle under pressure. They are held in a wire cage known as a muselet or a muzzle.
How are still wine and sparkling wine corks made?
Still Wine Corks
Still wine corks are typically 24 to 25 millimeters (0.94 to 0.98 inches) in diameter. The length varies and generally depends on the estimated length of time the wine will ripen. Simple wines are usually 38 millimeters (1.5 inches) long, medium-aged wines (the most popular size) are 44 millimeters (1.7 inches) long, and long-aged or expensive wines are often 49-55 millimeters (1.9-2.2 inches) long.
Sparkling Wine Corks
The corkscrew for sparkling wine is typically 30 millimeters (1.2 inches) in diameter and 50 millimeters (2.0 inches) long. When bottled, the cork is compressed to about 60-70% of its original diameter. The cork in sparkling wine mostly consists of three sections and is called agglomerated cork. The mushroom morphology that occurs in the transition consists of two stacked discs of clean cork glued to the top, the bottom being an aggregate of crushed cork and glue. The lower part of the cork comes in contact with the wine. The cork of sparkling wine before insertion is about 50% larger than the bottle entrance. The cork is compressed before it is inserted into the neck of the sparkling wine bottle. Over time, this compressed form of the cork becomes permanent, resulting in its mushroom shape.
The quality of wine corks
Cork is moisture resistant, slow to stagnation, helps prevent wine ripening, and provides a waterproof seal. Stoppers are associated with a perception of high-quality wines, as they are generally cheaper alternatives, especially for low-priced wines. Due to its cellular structure, cork can easily be compressed and expanded to form a solid seal once it is fitted. The inner diameter of the neck of a glass bottle tends to be inconsistent, making this ability to seal through various shrinkages and expansions an important attribute. However, the cork itself is very inconsistent due to unavoidable natural defects, channels, and cracks in the bark. In a closure study in 2005, 45% of corks showed gas leaks through the sides of the cork and the cork itself during the pressure test.
The reusability of wine corks
Many synthetic corks can be recycled at home, but natural corks can be composted or recycled at specific stores. The company receives the cork used in cooperation with the store and recycles it to make other products. Re-Cork is the largest of these companies in the United States. Cork is also widely reused in arts and crafts.
Different types of wine corks
As you can imagine, various types of wine corks are produced to preserve different types of wines. In this section, we’ll take a look at some of them. The Natural Cork is made from a single hull, offers maximum flexibility, and keeps the seal strong for aging wines for more than five years. Although the cork is made from a single piece of a cell, the pores are filled with glue and cork dust. The addition of glue and cork dust makes it easy to take the cork out of the bottle and is also suitable for medium ripening. The Multi-piece Cork is two or more pieces glued together. They are denser than integral cork and are not suitable for long-term aging. The Agglomerated Cork is made of cork dust and glue; it is dense, inexpensive, and not suitable for sealing wine for more than a year. The Technical Cork is a cohesive cork with a single cork on either side.
Conclusion
In this article, we learned that cork does not absorb water or any other liquid, because of which it has been used as a wine stopper for hundreds of years. It is also used in buoys, life jackets, and other buoyancy devices and can remain buoyant for years. Additionally, we also learned that cork, because it’s made from the bark of the cork oak tree, is a natural, reusable, and recyclable material.
