Cork (material)

<h2 id="history">History</h2>

Cork is a natural material used by humans for over 5,000 years. It is a material whose applications have been known since <a href="/facts/Ancient_history/P0fFQ8z5">antiquity</a>, especially in floating devices and as stopper for <a href="/facts/Beverages/anzgxSCt">beverages</a>, mainly <a href="/facts/Wine/przCrC98">wine</a>, whose market, from the early twentieth century, had a massive expansion, particularly due to the development of several cork-based agglomerates.<a class="footnote-ref" id="fnref:4" href="#fn:4">4</a>
In <a href="/facts/China/lTjIXY5p">China</a>, <a href="/facts/Egypt/8Ttg0JwB">Egypt</a>, <a href="/facts/Babylon/Iz0TwTXS">Babylon</a>, and <a href="/facts/Persia/24yukge8">Persia</a> from about 3000 BC, cork was already used for sealing <a href="/facts/Container/yDfwMWvW">containers</a>, fishing equipment, and domestic applications. In <a href="/facts/Ancient_Greece/PTVBrWXq">ancient Greece</a> (1600 to 1100 years BC) cork was used in <a href="/facts/Footwear/JgvYYCSS">footwear</a>, to manufacture a type of <a href="/facts/Sandal/F4503auG">sandals</a> attached to the foot by straps, generally <a href="/facts/Leather/kvQtwHPH">leather</a> and with a sole in cork or leather.<a class="footnote-ref" id="fnref:5" href="#fn:5">5</a><a class="footnote-ref" id="fnref:6" href="#fn:6">6</a>
In the second century AD, a Greek physician, <a href="/facts/Dioscorides/FzDmURv3">Dioscorides</a>, noted several medical applications of cork, mainly for hair loss treatment.<a class="footnote-ref" id="fnref:7" href="#fn:7">7</a> Nowadays, the majority of people know cork for its use as stoppers in <a href="/facts/Wine/przCrC98">wine</a> <a href="/facts/Bottle/TfyKYYKb">bottles</a>. The innovation of using cork as stopper can be traced back to the late 17th century, attributed to <a href="/facts/Dom_P%C3%A9rignon_(monk)/1ahwzsyd">Dom Pierre Pérignon</a>.<a class="footnote-ref" id="fnref:8" href="#fn:8">8</a> Cork stoppers were adopted in 1729 by <a href="/facts/Ruinart_(Champagne)/33T8bmEz">Ruinart</a> and in 1973 by <a href="/facts/Mo%C3%ABt_%26_Chandon/oRYbvUUr">Moët et Chandon</a>.<a class="footnote-ref" id="fnref:9" href="#fn:9">9</a>

<h2 id="structure">Structure</h2>
Cork presents a characteristic cellular structure in which the <a href="/facts/Cell_(biology)/bLM9UQvy">cells</a> have usually a pentagonal or hexagonal shape. The cellular wall consists of a thin, lignin-rich middle <a href="/facts/Lamella_(cell_biology)/8FDJz8WQ">lamella</a> (internal primary wall), a thick secondary wall made up from alternating suberin and wax lamella, and a thin tertiary wall of polysaccharides. Some studies suggest that the secondary wall is lignified, and therefore, may not consist exclusively of suberin and waxes. The cells of cork are filled with a <a href="/facts/Gas/hVVAoodV">gas</a> <a href="/facts/Mixture/tms8rbmn">mixture</a> similar to air, making them behave as authentic "pads," which contributes to the capability of cork to recover after compression.<a class="footnote-ref" id="fnref:10" href="#fn:10">10</a>

<h2 id="sources">Sources</h2>

There are about 2,200,000 hectares of cork oak (<a href="/facts/Quercus_suber/szFesMGD">Quercus suber</a>) forest in the <a href="/facts/Mediterranean_basin/azjFD5mW">Mediterranean basin</a>, the native area of the species. The most extensively managed habitats are in <a href="/facts/Portugal/lYzwDQ63">Portugal</a> (34%) and in <a href="/facts/Spain/bIyrB8EY">Spain</a> (27%).
Annual production is about 300,000 tons; 49.6% from Portugal, 30.5% from Spain, 5.8% from <a href="/facts/Morocco/6ly8170M">Morocco</a>, 4.9% from <a href="/facts/Algeria/UXDF4Tj6">Algeria</a>, 3.5% from <a href="/facts/Tunisia/4uC8Po6k">Tunisia</a>, 3.1% from <a href="/facts/Italy/tUf0PDYF">Italy</a>, and 2.6% from <a href="/facts/France/CxIeIKM3">France</a>.<a class="footnote-ref" id="fnref:11" href="#fn:11">11</a>
Once the trees are about 25 years old the cork is traditionally stripped from the trunks every nine years, with the first two harvests generally producing lower quality cork (male cork or virgin cork). The trees live for about 300 years.
The cork industry is generally regarded as environmentally friendly.<a class="footnote-ref" id="fnref:12" href="#fn:12">12</a> Cork production is generally considered <a href="/facts/Sustainable/9oYH9mAs">sustainable</a> because the cork tree is not cut down to obtain cork; only the bark is stripped to harvest the cork.<a class="footnote-ref" id="fnref:13" href="#fn:13">13</a> The tree continues to live and grow. The <a href="/facts/Sustainability/9oYH9mAs">sustainability</a> of production and the easy <a href="/facts/Recycling/x9X7GAzz">recycling</a> of cork products and by-products are two of its most distinctive aspects. <a href="/facts/Cork_oak/szFesMGD">Cork oak</a> forests also prevent <a href="/facts/Desertification/N7rdrzFy">desertification</a> and are a particular habitat in the <a href="/facts/Iberian_Peninsula/ztFXI8zt">Iberian Peninsula</a> and the refuge of various <a href="/facts/Endangered_species/L7cIweSW">endangered species</a>.<a class="footnote-ref" id="fnref:14" href="#fn:14">14</a>
<a href="/facts/Carbon_footprint/gRb1RaQl">Carbon footprint</a> studies conducted by <a href="/facts/Corticeira_Amorim/eJNoEFUT">Corticeira Amorim</a>, Oeneo Bouchage of France and the Cork Supply Group of Portugal concluded that cork is the most environmentally friendly <a href="/facts/Wine/przCrC98">wine</a> <a href="/facts/Stopper_(plug)/5YN0vlYt">stopper</a> in comparison to other alternatives. The <a href="/facts/Corticeira_Amorim/eJNoEFUT">Corticeira Amorim</a>'s study, in particular ("Analysis of the life cycle of Cork, Aluminum and Plastic Wine Closures"), was developed by <a href="/facts/PricewaterhouseCoopers/4AuXcnh0">PricewaterhouseCoopers</a>, according to <a href="/facts/ISO_14000/hGbSpvrC">ISO 14040</a>.<a class="footnote-ref" id="fnref:15" href="#fn:15">15</a><a class="footnote-ref" id="fnref:16" href="#fn:16">16</a> Results concluded that, concerning the emission of greenhouse gases, each plastic stopper released 10 times more <a href="/facts/Carbon_dioxide/xGzpppEp">CO2</a>, whilst an aluminium screw cap releases 26 times more CO2 than does a cork stopper. For example, to produce 1,000 cork stoppers 1.5 kg CO2 are emitted, but to produce the same amount of plastic stoppers 14 kg of CO2 are emitted and for the same amount of aluminium screw caps 37 kg CO2 are emitted.<a class="footnote-ref" id="fnref:17" href="#fn:17">17</a>
The <a href="/facts/Quercus_variabilis/8Fe56vRx">Chinese cork oak</a> is native to East Asia and is cultivated in a limited extent in China; the cork produced is considered inferior to Q. suber and are used to produce agglomerated cork products.<a class="footnote-ref" id="fnref:18" href="#fn:18">18</a>
The so-called "cork trees" (<a href="/facts/Phellodendron/VYVnMxm4">Phellodendron</a>) are unrelated to the cork oak, they have corky bark but not thick enough for cork production.

<h2 id="harvesting">Harvesting</h2>

Cork is extracted only from early May to late August, when the cork can be separated from the tree without causing permanent damage. When the tree reaches 25–30 years of age and about 24 in (60 cm) in circumference, the cork can be removed for the first time. However, this first harvest almost always produces poor quality or virgin cork (Portuguese cortiça virgem; Spanish corcho bornizo or corcho virgen<a class="footnote-ref" id="fnref:19" href="#fn:19">19</a>).
The workers who specialize in removing the cork are known as extractors. An extractor uses a very sharp axe to make two types of cuts on the tree: one horizontal cut around the plant, called a crown or necklace, at a height of about two to three times the circumference of the tree, and several vertical cuts called rulers or openings. This is the most delicate phase of the work because, even though cutting the cork requires significant force, the extractor must not damage the underlying <a href="/facts/Phellogen/7MvQF7ss">phellogen</a> or the tree will be harmed.
To free the cork from the tree, the extractor pushes the handle of the axe into the rulers. A good extractor needs to use a firm but precise touch in order to free a large amount of cork without damaging the product or tree.

These freed portions of the cork are called planks. The planks are usually carried off by hand since cork forests are rarely accessible to vehicles. The cork is stacked in piles in the forest or in yards at a factory and traditionally left to dry, after which it can be loaded onto a truck and shipped to a processor.
Bark from initial harvests can be used to make flooring, shoes, insulation and other industrial products. Subsequent extractions usually occur at intervals of nine years, though it can take up to thirteen for the cork to reach an acceptable size. If the product is of high quality it is known as gentle cork (Portuguese cortiça amadia,<a class="footnote-ref" id="fnref:20" href="#fn:20">20</a> but also cortiça secundeira only if it is the second time; Spanish corcho segundero, also restricted to the second time<a class="footnote-ref" id="fnref:21" href="#fn:21">21</a>), and, ideally, is used to make stoppers for wine and champagne bottles.<a class="footnote-ref" id="fnref:22" href="#fn:22">22</a>

<h2 id="properties-and-uses">Properties and uses</h2>

Cork's <a href="/facts/Elasticity_(solid_mechanics)/wcJoIFg1">elasticity</a> combined with its near-impermeability makes it suitable as a material for <a href="/facts/Bottle/TfyKYYKb">bottle</a> <a href="/facts/Stopper_(plug)/5YN0vlYt">stoppers</a>, especially for <a href="/facts/Wine_bottle/pXWQb5S6">wine bottles</a>. Cork stoppers represent about 60% of all cork based production. Cork has an almost zero <a href="/facts/Poisson%27s_ratio/ppIsaujA">Poisson's ratio</a>, which means the radius of a cork does not change significantly when squeezed or pulled.<a class="footnote-ref" id="fnref:23" href="#fn:23">23</a>
Cork is an excellent <a href="/facts/Gasket/gQ3bnuPK">gasket</a> material. Some <a href="/facts/Carburetor/DMvC7y9M">carburetor</a> float bowl gaskets are made of cork, for example.
Cork is also an essential element in the production of <a href="/facts/Badminton/abkzqM3h">badminton</a> <a href="/facts/Shuttlecock/vQXmEFp8">shuttlecocks</a>.<a class="footnote-ref" id="fnref:24" href="#fn:24">24</a>
Cork's bubble-form structure and natural fire retardant make it suitable for acoustic and <a href="/facts/Cork_thermal_insulation/HLTRWz2d">thermal insulation</a> in house walls, floors, ceilings, and facades. The by-product of more lucrative stopper production, corkboard, is gaining popularity as a non-allergenic, easy-to-handle and safe alternative to petrochemical-based insulation products.
Cork is also used to make vinyl record slipmats, due to its ability to not attract dust. They also dampen static and vibrations.<a class="footnote-ref" id="fnref:25" href="#fn:25">25</a>
Sheets of cork, also often the by-product of stopper production, are used to make <a href="/facts/Bulletin_boards/Lndt9fLG">bulletin boards</a> as well as <a href="/facts/Flooring/h0DhmqTp">floor and wall tiles</a>.
Cork's low <a href="/facts/Density/92p6hh9I">density</a> makes it a suitable material for <a href="/facts/Fishing/EBVEPvhI">fishing</a> <a href="/facts/Float_(fishing)/rCqLXVwC">floats</a> and buoys, as well as handles for <a href="/facts/Fishing_rod/uef65wdk">fishing rods</a> (as an alternative to <a href="/facts/Neoprene/MtLEdFvE">neoprene</a>).
Granules of cork can also be mixed into <a href="/facts/Concrete/K6whGVNx">concrete</a>. The composites made by mixing cork granules and cement have lower thermal conductivity, lower density, and good energy absorption. Some of the property ranges of the composites are density (400–1500 kg/m3), compressive strength (1–26 MPa), and flexural strength (0.5–4.0 MPa).<a class="footnote-ref" id="fnref:26" href="#fn:26">26</a>

<h3>Use in wine bottling</h3>

As late as the mid-17th century, French <a href="/facts/Vintners/7Gp6z2Nj">vintners</a> did not use cork stoppers, using instead oil-soaked rags stuffed into the necks of bottles.<a class="footnote-ref" id="fnref:27" href="#fn:27">27</a>
Wine corks can be made of either a single piece of cork, or composed of particles, as in champagne corks; corks made of granular particles are called "agglomerated corks".<a class="footnote-ref" id="fnref:28" href="#fn:28">28</a>
Natural cork <a href="/facts/Closure_(wine_bottle)/Lg3Psfcd">closures</a> are used for about 80% of the 20 billion bottles of <a href="/facts/Wine/przCrC98">wine</a> produced each year. After a decline in use as wine-stoppers due to the increase in the use of synthetic alternatives, cork wine-stoppers are making a comeback and currently represent approximately 60% of wine-stoppers in 2016.<a class="footnote-ref" id="fnref:29" href="#fn:29">29</a>

Because of the cellular structure of cork, it is easily compressed upon insertion into a bottle and will expand to form a tight seal. The interior diameter of the neck of glass bottles tends to be inconsistent, making this ability to seal through variable contraction and expansion an important attribute. However, unavoidable natural flaws, channels, and cracks in the bark make the cork itself highly inconsistent. In a 2005 closure study, 45% of corks showed gas leakage during pressure testing both from the sides of the cork as well as through the cork body itself.<a class="footnote-ref" id="fnref:30" href="#fn:30">30</a>

Since the mid-1990s, a number of wine brands have switched to <a href="/facts/Alternative_wine_closure/mqqKjj0H">alternative wine closures</a> such as <a href="/facts/Plastic/Kla5QItn">plastic</a> stoppers, <a href="/facts/Screw_cap_(wine)/0k5V9Iu6">screw caps</a>, or other closures. During 1972 more than half of the Australian bottled wine went bad due to corking. A great deal of anger and suspicion was directed at Portuguese and Spanish cork suppliers who were suspected of deliberately supplying bad cork to non-<a href="/facts/European_Economic_Community/tx2V9KAQ">EEC</a> wine makers to help prevent cheap imports. Cheaper wine makers developed the aluminium "Stelvin" cap with a polypropylene stopper wad. More expensive wines and carbonated varieties continued to use cork, although much closer attention was paid to the quality. Even so, some high premium makers prefer the Stelvin as it is a guarantee that the wine will be good even after many decades of ageing. Some consumers may have conceptions about screw caps being representative of lower quality wines, due to their cheaper price; however, in Australia, for example, much of the non-sparkling wine production now uses these Stelvin caps as a cork alternative, although some have recently switched back to cork citing issues using screw caps.<a class="footnote-ref" id="fnref:31" href="#fn:31">31</a>

The alternatives to cork have both advantages and disadvantages. For example, screwtops are generally considered to offer a <a href="/facts/Cork_taint/vPdXWQr4">trichloroanisole</a> (TCA) free seal, but they also reduce the oxygen transfer rate between the bottle and the atmosphere to almost zero, which can lead to a reduction in the quality of the wine. TCA is the main documented cause of <a href="/facts/Cork_taint/vPdXWQr4">cork taint</a> in wine. However, some in the wine industry say natural cork stoppers are important because they allow oxygen to interact with wine for proper aging, and are best suited for wines purchased with the intent to age.<a class="footnote-ref" id="fnref:32" href="#fn:32">32</a>
Stoppers which resemble natural cork very closely can be made by isolating the suberin component of the cork from the undesirable <a href="/facts/Lignin/CdaxpB3b">lignin</a>, mixing it with the same substance used for contact lenses and an adhesive, and molding it into a standardized product, free of TCA or other undesirable substances.<a class="footnote-ref" id="fnref:33" href="#fn:33">33</a> Composite corks with real cork veneers are used in cheaper wines.<a class="footnote-ref" id="fnref:34" href="#fn:34">34</a> Celebrated Australian wine writer and critic <a href="/facts/James_Halliday_(wine)/UJvbJnv9">James Halliday</a> has written that since a cork placed inside the neck of a wine bottle is 350-year-old technology, it is logical to explore other more modern and precise methods of keeping wine safe.<a class="footnote-ref" id="fnref:35" href="#fn:35">35</a>
The study "Analysis of the life cycle of Cork, Aluminum and Plastic Wine Closures," conducted by <a href="/facts/PricewaterhouseCoopers/4AuXcnh0">PricewaterhouseCoopers</a> and commissioned by a major cork manufacturer, <a href="/facts/Corticeira_Amorim/eJNoEFUT">Amorim</a>, concluded that cork is the most environmentally responsible stopper, in a one-year <a href="/facts/Life_cycle_assessment/vGKCvfYf">life cycle analysis</a> comparison with plastic stoppers and aluminum screw caps.<a class="footnote-ref" id="fnref:36" href="#fn:36">36</a><a class="footnote-ref" id="fnref:37" href="#fn:37">37</a>

<h3>Other uses</h3>

<ul><li>On 28 November 2007, the Portuguese national postal service <a href="/facts/CTT_Correios_de_Portugal,_S.A./UkMBj17c">CTT</a> issued the world's first <a href="/facts/Postage_stamp/T8gb7wCP">postage stamp</a> made of cork.<a class="footnote-ref" id="fnref:38" href="#fn:38">38</a><a class="footnote-ref" id="fnref:39" href="#fn:39">39</a></li>
<li>In musical instruments, particularly <a href="/facts/Woodwind_instrument/JBMxaxyM">woodwind instruments</a>, where it is used to fasten together segments of the instrument, making the seams airtight. Low quality conducting baton handles are also often made out of cork.</li>
<li>In shoes, especially those using <a href="/facts/Welt_(shoe)/c29INVBI">welt construction</a> to improve climate control and comfort.</li>
<li>Because it is impermeable and moisture-resistant, cork is often used as an alternative to leather in <a href="/facts/Handbag/xE6T441X">handbags</a>, <a href="/facts/Wallet/RJlroKpG">wallets</a>, and other fashion items.</li>
<li>To make <a href="/facts/Brick/2CBPgDIK">bricks</a> for the outer walls of houses, as in Portugal's pavilion at <a href="/facts/Expo_2000/l0Nztz0F">Expo 2000</a>.</li>
<li>As the core of both <a href="/facts/Baseball_(ball)/U2033ze4">baseballs</a> and <a href="/facts/Cricket_ball/yTXzw0x7">cricket balls</a>. A <a href="/facts/Corked_bat/3FuAdIWg">corked bat</a> is made by replacing the interior of a <a href="/facts/Baseball_bat/XDS93stu">baseball bat</a> with cork – a practice known as "corking". It was historically a method of cheating at <a href="/facts/Baseball/42bEQy1Y">baseball</a>; the efficacy of the practice is now discredited.</li>
<li>In various forms, in spacecraft <a href="/facts/Heat_shield/YvRhkzAz">heat shields</a><a class="footnote-ref" id="fnref:40" href="#fn:40">40</a> and <a href="/facts/Payload_fairing/V1UezFkV">fairings</a>.</li>
<li>In the paper pick-up mechanisms in <a href="/facts/Inkjet/YWnIfRmG">inkjet</a> and <a href="/facts/Laser_printers/fJ2GrUBj">laser printers</a>.</li>
<li>To make later-model <a href="/facts/Pith_helmet/Qv4rHTJW">pith helmets</a>.<a class="footnote-ref" id="fnref:41" href="#fn:41">41</a></li>
<li>Hung from hats to keep insects away. (See <a href="/facts/Cork_hat/LsR857y8">cork hat</a>)</li>
<li>As a core material in <a href="/facts/Sandwich_structured_composite/H8MRmL2H">sandwich composite</a> construction.</li>
<li>As the friction lining material of an <a href="/facts/Automatic_transmission/bKBFLbyh">automatic transmission</a> <a href="/facts/Clutch/yQLCtuGA">clutch</a>, as designed in certain <a href="/facts/Mopeds/KraM4ID2">mopeds</a>.</li>
<li>Alternative of wood or aluminium in automotive interiors.<a class="footnote-ref" id="fnref:42" href="#fn:42">42</a></li>
<li>Cork slabs are sometimes used by orchid growers as a natural mounting material.</li>
<li>Cork paddles are used by glass blowers to manipulate and shape hot molten glass.</li>
<li>Many racing bicycles have their handlebars wrapped in cork-based tape manufactured in a variety of colors.</li>
<li>To make <a href="/facts/Architectural_model/V4BIV4hQ">architectural models</a>.</li></ul>
<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Bung/5YN0vlYt">Bung</a></li>
<li><a href="/facts/Cork_Boat_(vessel)/D6f0oXLp">Cork Boat (vessel)</a></li>
<li><a href="/facts/Cork_borer/AAHSXjGV">Cork borer</a></li>
<li><a href="/facts/Cork_cambium/7MvQF7ss">Cork cambium</a></li>
<li><a href="/facts/Corkscrew_(tool)/mv1jpFLb">Corkscrew</a></li>
<li><a href="/facts/Cricket_ball/yTXzw0x7">Cricket ball</a></li></ul>

<h2 id="notes">Notes</h2>

<ul><li>Margarida Pi i Contallé. 2006. Laboratory head in <a href="http://manuelserrataponesdecorcho.blogspot.com/">Manuel Serra</a> <a href="https://web.archive.org/web/20110721040429/http://www.tesisenxarxa.net/TESIS_UAB/AVAILABLE/TDX-1031107-165146/mpc1de1.pdf">Hongos y micotoxinas en tapones de corcho. Propuesta de límites micológicos aceptables</a></li>
<li><a href="http://www.corkfacts.com/natlcrk11.htm">Cork production</a> corkfacts.com</li>
<li><a href="https://web.archive.org/web/20160408013152/http://www.iprocor.org/">Instituto de Promoción del Corcho, Extremadura</a> iprocor.org (in Spanish)</li>
<li><a href="https://web.archive.org/web/20090913143609/http://www.corkfacts.com/pdffiles/Amorim_LCA_Final_Report.pdf">Analysis of the life cycle of Cork, Aluminium and Plastic Wine Closures</a></li>
<li>Henley, Paul, BBC.com (18 September 2008). <a href="http://news.bbc.co.uk/2/hi/europe/7623912.stm">"Urging vintners to put a cork in it"</a>.</li>
<li><a href="/facts/PricewaterhouseCoopers/4AuXcnh0">PricewaterhouseCoopers</a>/ECOBILAN (October 2008). <a href="https://web.archive.org/web/20090913143609/http://www.corkfacts.com/pdffiles/Amorim_LCA_Final_Report.pdf">Analysis of the life cycle of Cork, Aluminium and Plastic Wine Closures</a></li>
<li><a href="https://www.bbc.co.uk/programmes/b00g34qr">Cork - Forest in a Bottle.</a> 2008.</li></ul>
<h2 id="external-links">External links</h2>

Wikimedia Commons has media related to Cork (material).

<ul><li><a href="http://www.corkqc.com/">Cork Quality Council</a></li>
<li><a href="http://www.vinography.com/archives/2008/05/book_review_to_cork_or_not_to.html">Book review: To cork or not to cork </a></li>
<li><a href="http://www.makeitfrom.com/data/?material=Cork">Material Properties Data: Cork</a></li>
<li><a href="http://www.corkclub.com">Cork Recycling Initiative.</a> 2017.</li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1">Calheiros, J. L.; Meneses, E. "The cork industry in Portugal". Junta Nacional da Cortiça, Portugal. Archived from the original on 12 January 2012. <a href="https://web.archive.org/web/20120112090704/http://www.uwec.edu/Geography/Ivogeler/Travel/Portugal/cork-article2.htm" target="_blank">https://web.archive.org/web/20120112090704/http://www.uwec.edu/Geography/Ivogeler/Travel/Portugal/cork-article2.htm</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></li>
<li id="fn:2">"Robert Hooke (1635-1703)". UC Museum of Paleontology @ UC Berkeley. Retrieved 10 December 2022. <a href="http://www.ucmp.berkeley.edu/history/hooke.html" target="_blank">http://www.ucmp.berkeley.edu/history/hooke.html</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></li>
<li id="fn:3">Duarte, Ana Paula; Bordado, João Carlos (2015). "Cork – A Renewable Raw Material: Forecast of Industrial Potential and Development Priorities". Frontiers in Materials. 2: 2. Bibcode:2015FrMat...2....2D. doi:10.3389/fmats.2015.00002. ISSN 2296-8016. Text was copied from this source, which is available under a Creative Commons Attribution 4.0 International License. <a href="https://doi.org/10.3389%2Ffmats.2015.00002" target="_blank">https://doi.org/10.3389%2Ffmats.2015.00002</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></li>
<li id="fn:4">Gil, Luís (11 April 2014). "Cork: a strategic material". Frontiers in Chemistry. 2: 16. Bibcode:2014FrCh....2...16G. doi:10.3389/fchem.2014.00016. ISSN 2296-2646. PMC 3990040. PMID 24790984. Text was copied from this source, which is available under a Creative Commons Attribution 4.0 International License. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3990040" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3990040</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></li>
<li id="fn:5">"Cork: culture, nature, future". Santa Maria de Lamas: Press Release. APCOR Cork Information Bureau (Facebook: CorkInWorld). 2010. Retrieved 10 December 2022. <a href="https://www.youtube.com/watch?v=4JqCLi07ghY" target="_blank">https://www.youtube.com/watch?v=4JqCLi07ghY</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></li>
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<li id="fn:20">Amadio comes from and is a synonym of amavio, "beberage or spell to seduce" (Dicionário Houaiss da Língua Portuguesa), from amar, "to love". <a href="#fnref:20" class="footnote-back-ref">↩</a></li>
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</ol>

Cork (material) open-in-new

Cork (material)