{"id":16829,"date":"2025-12-16T16:34:43","date_gmt":"2025-12-16T15:34:43","guid":{"rendered":"https:\/\/www.rct-online.de\/magazin\/?p=16829"},"modified":"2026-09-02T10:23:40","modified_gmt":"2026-09-02T08:23:40","slug":"lime-and-limestone-as-natural-material","status":"publish","type":"post","link":"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/","title":{"rendered":"Lime and Limestone: Key facts about the natural material"},"content":{"rendered":"<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_73 ez-toc-wrap-center counter-hierarchy ez-toc-counter ez-toc-white ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of contents<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/#What_lime_is_and_where_it_is_found\" title=\"What lime is and where it is found\">What lime is and where it is found<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/#Unwelcome_lime_in_the_water_the_degree_of_hardness\" title=\"Unwelcome lime in the water: the degree of hardness\">Unwelcome lime in the water: the degree of hardness<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/#Where_does_lime_come_from_The_carbon_cycle\" title=\"Where does lime come from? The carbon cycle\">Where does lime come from? The carbon cycle<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/#Popular_building_material\" title=\"Popular building material\">Popular building material<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/#Everywhere_and_nowhere\" title=\"Everywhere and nowhere\">Everywhere and nowhere<\/a><\/li><\/ul><\/nav><\/div>\n<p style=\"text-align: justify;\"><b><span data-contrast=\"none\">Limescale deposits <\/span><\/b><b><span data-contrast=\"none\">on <\/span><\/b><b><span data-contrast=\"none\">chrome-plated or stainless steel fittings, and clouded tiles in the bathroom,<\/span><\/b><b><span data-contrast=\"none\"> are unsightly.<\/span><\/b><b> <\/b><b><span data-contrast=\"none\">I<\/span><\/b><b><span data-contrast=\"none\">n water heaters, in the coffee machine or in pipework, however, they cause problems, because they reduce heat transfer and impede the flow of water. But not all lime is the same.<\/span><\/b><\/p>\n<p style=\"text-align: justify;\"><b><span data-contrast=\"none\">Forestry businesses have lime spread over large areas of woodland to counteract the acidification of forest soils <\/span><\/b><b><span data-contrast=\"none\">\u2013 <\/span><\/b><b><span data-contrast=\"none\">and gardeners do exactly the same on their lawns. Limestone is likewise indispensable as a building material: marble was already used in antiquity for palaces, temples and sculptures that still fascinate us today. <strong>No less fascinating are<\/strong> the bizarre formations in limestone caves, <strong>the<\/strong> stalactites and stalagmites <strong>nature has shaped<\/strong> from lime over thousands of years, hidden from view. And the global climate, too, is substantially influenced by lime and its cycle in nature.<\/span><\/b><b><span data-contrast=\"none\"> Whether it is welcome or not, we encounter lime, this natural material, constantly and everywhere, and it plays a significant role in our lives.<\/span><\/b><\/p>\n<figure id=\"attachment_5868\" aria-describedby=\"caption-attachment-5868\" style=\"width: 415px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-5868\" title=\"Stalactites hanging in Treak Cliff Cavern in England\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/Haengende-Stalaktiten-in-der-englischen-Treak-Cliff-Cavern.jpg\" alt=\"stalactites hanging in treak cliff cavern england lime-natural-material\" width=\"415\" height=\"277\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/Haengende-Stalaktiten-in-der-englischen-Treak-Cliff-Cavern.jpg 600w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/Haengende-Stalaktiten-in-der-englischen-Treak-Cliff-Cavern-300x200.jpg 300w\" sizes=\"(max-width: 415px) 100vw, 415px\" \/><figcaption id=\"caption-attachment-5868\" class=\"wp-caption-text\"><center>Stalactites hanging in Treak Cliff Cavern in England<\/center><\/figcaption><\/figure>\n<h2><span class=\"ez-toc-section\" id=\"What_lime_is_and_where_it_is_found\"><\/span>What lime is and where it is found<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">Lime is calcium carbonate (CaCO<span data-contrast=\"none\"><sub>3<\/sub><\/span>), the calcium salt of carbonic acid (H<span data-contrast=\"none\"><sub>2<\/sub><\/span>CO<span data-contrast=\"none\"><sub>3<\/sub><\/span>), an acid that does not actually exist in this form, because it is unstable and decomposes into water and carbon dioxide (CO<span data-contrast=\"none\"><sub>2<\/sub><\/span>). It does, however, form stable salts: the carbonates, a class of chemical compounds. Lime occurs in nature in many different shapes and forms. The largest proportion is found in water as limestone, marine deposits that shellfish and corals, among others, helped to form.<\/p>\n<blockquote>\n<p style=\"text-align: justify;\">In the course of the Earth&#8217;s history, tectonic events have uplifted the world&#8217;s seabeds, from which entire mountain ranges eventually emerged, such as the Wetterstein Mountains in Europe or the Dolomites in the Limestone Alps.<\/p>\n<\/blockquote>\n<p style=\"text-align: justify;\">Marble is a particularly beautiful form of calcareous rock: crystalline, and formed later from limestone deposits deep in the Earth&#8217;s crust at high temperature and pressure. Processes like these, which take place over millions of years, are what mineralogists call \u201cmetamorphic transformations\u201d.<\/p>\n<figure id=\"attachment_5870\" aria-describedby=\"caption-attachment-5870\" style=\"width: 280px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-5870\" title=\"One of the best-known marble statues: Michelangelo's David\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/David-von-Michelangelo.jpg\" alt=\"Michelangelo's David\" width=\"280\" height=\"536\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/David-von-Michelangelo.jpg 600w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/David-von-Michelangelo-157x300.jpg 157w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/David-von-Michelangelo-535x1024.jpg 535w\" sizes=\"(max-width: 280px) 100vw, 280px\" \/><figcaption id=\"caption-attachment-5870\" class=\"wp-caption-text\"><center>One of the best-known marble statues: Michelangelo&#8217;s David<\/center><\/figcaption><\/figure>\n<p style=\"text-align: justify;\">The class of \u201cnatural\u201d carbonates also includes potassium carbonate (K<span data-contrast=\"none\"><sub>2<\/sub><\/span>CO<span data-contrast=\"none\"><sub>3<\/sub><\/span>), which goes by the historically derived common name \u201cpotash\u201d, and sodium carbonate (Na<span data-contrast=\"none\"><sub>2<\/sub><\/span>CO<span data-contrast=\"none\"><sub>3<\/sub><\/span>), better known as \u201csoda\u201d. These, and in some places lime as well, are constituents of salt deposits that were once formed as early seas evaporated.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Unwelcome_lime_in_the_water_the_degree_of_hardness\"><\/span>Unwelcome lime in the water: the degree of hardness<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">The grey, dull deposits on the shower wall and on the chrome-plated tap are familiar to everyone. The reason for them is the lime dissolved in the water, which is left behind when the water evaporates, just as it was when the primordial seas dried out.<\/p>\n<blockquote>\n<p style=\"text-align: justify;\">Depending on how much lime the water contains, a distinction is made between \u201chard\u201d and \u201csoft\u201d water, which can be observed from the different amounts of lather produced with soap.<\/p>\n<\/blockquote>\n<p style=\"text-align: justify;\">Plenty of lather means soft water with a low lime content, whereas little lather indicates hard water with a high lime content. This is because the lime dissolved in the water reacts with soaps (the sodium or potassium salts of long-chain carboxylic acids) to form sparingly soluble calcium salts: the \u201clime soaps\u201d. As a result, the readily water-soluble sodium or potassium soaps are no longer available for lather and the cleaning action that goes with it; indeed, lime soaps are also a constituent of the unwelcome limescale deposits in the bathroom.<\/p>\n<p><center><a href=\"https:\/\/www.rct-online.de\/en\/tubes-hoses\/tubings-and-pipes-made-of-rigid-plastics\/pe-tubing\/28744\/lldpe-tubing-for-drinking-water-supply\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-5877 size-full\" title=\"LLDPE hose for drinking water supply\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/lldpe-schlauch-fuer-die-trinkwasserversorgung.jpg\" alt=\"lldpe-hose-for-drinking-water-supply\" width=\"300\" height=\"300\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/lldpe-schlauch-fuer-die-trinkwasserversorgung.jpg 300w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/lldpe-schlauch-fuer-die-trinkwasserversorgung-150x150.jpg 150w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a> <a href=\"https:\/\/www.rct-online.de\/en\/tubes-hoses\/tubing-made-of-elastomers-soft-rubber\/nbr-tubing\/28557\/nbr-drinking-water-tubing-ktw\/dvgw\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-5878 size-full\" title=\"NBR drinking water hose - KTW\/DVGW\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/nbr-trinkwasserschlauch-ktw-dvgw.jpg\" alt=\"nbr-drinking-water-hose-ktw-dvgw\" width=\"300\" height=\"300\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/nbr-trinkwasserschlauch-ktw-dvgw.jpg 300w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/nbr-trinkwasserschlauch-ktw-dvgw-150x150.jpg 150w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><\/center><\/p>\n<p style=\"text-align: justify;\">Water hardness naturally depends on where the water comes from. Mountain water contains more minerals (potassium and calcium, for example) and therefore more lime, making it harder than drinking water obtained by riverbank filtration. In Germany, the hardness of water is defined as the calcium oxide content (CaO) in millimoles of calcium oxide per litre of water and stated in \u201cdegrees of German hardness\u201d (\u00b0dH).<\/p>\n<figure id=\"attachment_5873\" aria-describedby=\"caption-attachment-5873\" style=\"width: 375px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-5873\" title=\"Limescale deposits on a leaking shut-off valve\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/Kalkablagerungen-an-einem-undichten-Absperrventil.jpg\" alt=\"limescale deposits on a leaking shut-off valve lime-natural-material\" width=\"375\" height=\"369\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/Kalkablagerungen-an-einem-undichten-Absperrventil.jpg 600w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/Kalkablagerungen-an-einem-undichten-Absperrventil-300x295.jpg 300w\" sizes=\"(max-width: 375px) 100vw, 375px\" \/><figcaption id=\"caption-attachment-5873\" class=\"wp-caption-text\"><center>Limescale deposits on a leaking shut-off valve<\/center><\/figcaption><\/figure>\n<p style=\"text-align: justify;\">On this scale, water with a calcium oxide content of up to 1.3 mmol\/l, corresponding to a water hardness of up to 7 \u00b0dH, is \u201csoft\u201d water. Water with a calcium oxide content of more than 2.5 mmol\/l, by contrast, is \u201chard\u201d water, corresponding to a hardness above 14 \u00b0dH. A rule of thumb that is easier to remember: one degree of German water hardness (1 \u00b0dH) corresponds to 10 mg of calcium oxide per litre of water. Yet all these figures are likely to interest only a few: the layperson senses water hardness when doing the laundry and showering, or recognises it from the scale deposits in the kettle.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Where_does_lime_come_from_The_carbon_cycle\"><\/span>Where does lime come from? The carbon cycle<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">Because of the carbon contained in the carbonate, lime is part of the geological carbon cycle in the non-living world and, as a natural material, one of many carbon reservoirs. Although carbon occurs in comparatively small quantities on our planet, at 0.03 %, it is a crucial element for the climate. Some 99 % of all carbon by mass is fixed in sediments, largely in carbonates and therefore also in the natural material lime.<\/p>\n<blockquote>\n<p style=\"text-align: justify;\">When calcareous rock weathers, atmospheric CO<span data-contrast=\"none\"><sub>2<\/sub><\/span> dissolved in water, in rainwater for example, converts the insoluble calcium carbonate CaCO<span data-contrast=\"none\"><sub>3<\/sub><\/span> into soluble calcium hydrogen carbonate Ca(HCO<span data-contrast=\"none\"><sub>3<\/sub><\/span>)<span data-contrast=\"none\"><sub>2<\/sub><\/span>.<\/p>\n<\/blockquote>\n<p style=\"text-align: justify;\">This mobilises calcium carbonate from the rock, and the water carries it away. Leaching of this kind is also how lime finds its way into our drinking water, where it is ultimately responsible for water hardness. Under altered external conditions, such as different temperatures, the hydrogen carbonate can convert straight back into carbon dioxide and calcium carbonate, and the latter is then deposited as a solid.<\/p>\n<p><center><a href=\"https:\/\/www.rct-online.de\/en\/tube-hose-connectors\/connectors-made-of-plastic\/barb-connectors\/28957\/water-flow-regulating-adapter\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-5881 size-full\" title=\"Water regulating adapter | no scaling of the adapter\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/wasser-regulier-uebergangsstueck.jpg\" alt=\"water regulating adapter \" width=\"300\" height=\"300\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/wasser-regulier-uebergangsstueck.jpg 300w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/wasser-regulier-uebergangsstueck-150x150.jpg 150w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a> <a href=\"https:\/\/www.rct-online.de\/en\/laboratory-equipment\/laboratory-equipment-and-utensils\/29894\/water-bath-made-of-pp\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-5882 size-full\" title=\"PP water bath | no lime build-up possible\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/wasserbad-aus-pp.jpg\" alt=\"pp water bath no lime build-up possible\" width=\"300\" height=\"300\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/wasserbad-aus-pp.jpg 300w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/wasserbad-aus-pp-150x150.jpg 150w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><\/center><\/p>\n<p style=\"text-align: justify;\">In the form of hydrogen carbonate, lime finally also makes its way via the rivers into the seas. Microorganisms, shellfish and corals use it to build their exoskeletons, which, after the organisms die, settle on the seabed as carbonate sediment.<\/p>\n<blockquote>\n<p style=\"text-align: justify;\">If the proportion of carbon dioxide in the atmosphere increases, the CO<span data-contrast=\"none\"><sub>2<\/sub><\/span> concentration in the world&#8217;s oceans rises as well.<\/p>\n<\/blockquote>\n<p style=\"text-align: justify;\">More carbon dioxide consequently dissolves in them and the seas begin to \u201cacidify\u201d. The consequences for marine flora and fauna are far-reaching, because these organisms are then no longer able to form the lime they need to build their skeletons. Forecasts state that the pH value, which normally averages pH = 8.25, will fall to 7.5 by the end of the century unless global countermeasures are taken and anthropogenic CO\u2082 emissions are reduced considerably.<\/p>\n<p><center><a href=\"https:\/\/www.rct-online.de\/en\/laboratory-equipment\/laboratory-containers\/measuring-beakers-and-measuring-flasks\/29798\/beaker-with-handle-made-of-pp-cylindrical-high\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-5885 size-full\" title=\"PP beaker with handle - cylindrical, tall\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/henkelbecher-aus-pp-zylindrisch-hoch.jpg\" alt=\"pp beaker with handle \u2013 cylindrical tall\" width=\"300\" height=\"300\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/henkelbecher-aus-pp-zylindrisch-hoch.jpg 300w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/henkelbecher-aus-pp-zylindrisch-hoch-150x150.jpg 150w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a> <a href=\"https:\/\/www.rct-online.de\/en\/laboratory-equipment\/laboratory-containers\/dishes-and-crucibles\/29778\/evaporating-dish-made-of-pp-with-spout\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-5886 size-full\" title=\"PP evaporating dish - with spout\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/abdampfschale-aus-pp-mit-ausguss.jpg\" alt=\"pp evaporating dish with spout\" width=\"300\" height=\"300\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/abdampfschale-aus-pp-mit-ausguss.jpg 300w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/abdampfschale-aus-pp-mit-ausguss-150x150.jpg 150w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><\/center><\/p>\n<h2><span class=\"ez-toc-section\" id=\"Popular_building_material\"><\/span>Popular building material<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">Like marble, lime has been known as a building material since antiquity. While marble can be quarried comparatively easily with muscle power, hammer and chisel and used directly, limestone as it is found in nature is not particularly well suited as a building material. It is porous and therefore less strong, and in our latitudes in particular it would quickly fall victim to weathering. To obtain a building material from natural limestone (CaCO<span data-contrast=\"none\"><sub>3<\/sub><\/span>), the stone has to be brought into a suitable chemical form. This is done in a two-stage conversion process, \u201clime burning\u201d and the subsequent \u201clime slaking\u201d \u2013 the product also being known as slaked lime.<\/p>\n<p style=\"text-align: justify;\">The limestone CaCO<span data-contrast=\"none\"><sub>3<\/sub><\/span> quarried and ground is first calcined at around +1000 \u00b0C in kiln-like plants, or \u201cburned\u201d as it is called, converting it into carbon dioxide and calcium oxide (CaO), the \u201cquicklime\u201d:<\/p>\n<p style=\"text-align: center;\"><span data-contrast=\"none\">Lime burning:<\/span> <span data-contrast=\"none\">CaCO<sub>3<\/sub><\/span><span data-contrast=\"none\"> \u2192<\/span> <span data-contrast=\"none\">CaO<\/span> <span data-contrast=\"none\">+<\/span> <span data-contrast=\"none\">CO<sub>2<\/sub><\/span><\/p>\n<p style=\"text-align: justify;\">Quicklime reacts exothermically with water, that is, with a vigorous release of heat, to form calcium hydroxide Ca(OH)<span data-contrast=\"none\"><sub>2<\/sub><\/span>, the strongly alkaline \u201cslaked lime\u201d:<\/p>\n<p style=\"text-align: center;\"><span data-contrast=\"none\">Lime slaking:<\/span> <span data-contrast=\"none\">CaO<\/span><span data-contrast=\"none\"> + H<sub>2<\/sub><\/span><span data-contrast=\"none\">O<\/span><span data-contrast=\"none\"> \u2192<\/span> <span data-contrast=\"none\">Ca<\/span><span data-contrast=\"none\">(OH)<sub>2<\/sub><\/span><\/p>\n<p style=\"text-align: justify;\">If slaked lime is mixed with sand, the result is lime mortar. As it sets, the slaked lime reacts with carbon dioxide from the air to form solid limestone once again, calcium carbonate (CaCO<span data-contrast=\"none\"><sub>3<\/sub><\/span>):<\/p>\n<p style=\"text-align: center;\"><span data-contrast=\"none\">Setting:<\/span> <span data-contrast=\"none\">Ca<\/span><span data-contrast=\"none\">(OH)<sub>2<\/sub><\/span> <span data-contrast=\"none\">+<\/span> <span data-contrast=\"none\">CO<sub>2<\/sub><\/span><span data-contrast=\"none\"> \u2192<\/span> <span data-contrast=\"none\">CaCO<sub>3<\/sub><\/span> <span data-contrast=\"none\">+<\/span> <span data-contrast=\"none\">H<sub>2<\/sub><\/span><span data-contrast=\"none\">O<\/span><\/p>\n<p style=\"text-align: justify;\">In the process, calcium carbonate forms finely crystalline structures which, together with angular crushed sand, produce a firm matrix and thus hold the masonry together. Today, lime mortar is used predominantly for the interior fit-out of buildings and, usually with further aggregates, as external render.<\/p>\n<figure id=\"attachment_5875\" aria-describedby=\"caption-attachment-5875\" style=\"width: 600px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-5875 size-full\" title=\"The technical lime cycle\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/Der-technische-Kalkkreislauf.jpg\" alt=\"the technical lime cycle lime-natural-material\" width=\"600\" height=\"321\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/Der-technische-Kalkkreislauf.jpg 600w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/Der-technische-Kalkkreislauf-300x161.jpg 300w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/Der-technische-Kalkkreislauf-310x165.jpg 310w\" sizes=\"(max-width: 600px) 100vw, 600px\" \/><figcaption id=\"caption-attachment-5875\" class=\"wp-caption-text\"><center>The technical lime cycle<\/center><\/figcaption><\/figure>\n<h2><span class=\"ez-toc-section\" id=\"Everywhere_and_nowhere\"><\/span>Everywhere and nowhere<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">Lime is omnipresent, as troublesome deposits in the bathroom and as the mineral constituent of drinking water that determines its hardness. In nature, however, we come to know its true beauty, in limestone ranges that rose from the early seas over the course of millions of years, and in caves and grottoes. Lime has been known as a building material since antiquity, as fine marble, as limestone and as quicklime for structures that still command our deep respect. Even today, the construction industry cannot do without lime. Its most important function, though, is as part of the inorganic carbon cycle, which matters so much for the world&#8217;s climate.<\/p>\n<p style=\"text-align: justify;\">The natural material lime is an all-rounder that plays its visible and invisible roles in many areas of everyday life and in nature.<\/p>\n<hr \/>\n<pre><strong>Image credits:<\/strong>\r\nFeatured image | \u00a9 Angela Staenicke \u2013 stock.adobe.com\r\nMichelangelo's David | \u00a9 Rico Heil (User:Silmaril) \u2013 de.wikipedia.org\r\nLimescale deposits on the shut-off valve | \u00a9 Richard Huber \u2013 commons.wikimedia.org\r\nTechnical lime cycle | \u00a9 H. Hoffmeister \u2013 de.wikipedia.org<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>Limescale deposits on chrome-plated or stainless steel fittings, and clouded tiles in the bathroom, are unsightly. In water heaters, in the coffee machine or in pipework, however, they cause problems, because they reduce heat transfer and impede the flow of water. But not all lime is the same. Forestry businesses have lime spread over large &hellip;<\/p>\n","protected":false},"author":15,"featured_media":12407,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1,2748],"tags":[4392,4387,4389,4386,2933,4393,3730,2774,4390,4391,4388],"class_list":["post-16829","post","type-post","status-publish","format-standard","has-post-thumbnail","","category-all-articles","category-materials-in-chemistry","tag-building-lime","tag-calcium-carbonate","tag-lime","tag-limescale-encrusted-tap","tag-lldpe-en","tag-marble","tag-nbr-en","tag-pp-en","tag-quicklime","tag-slaked-lime","tag-water-hardness-limestone"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v23.1 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Lime and Limestone: Key facts about the natural material<\/title>\n<meta name=\"description\" content=\"Lime is a popular natural and building material. All about its formation, uses and processing \u2705 Degree of water hardness \u2705 Carbon cycle.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Lime and Limestone: Key facts about the natural material\" \/>\n<meta property=\"og:description\" content=\"Lime is a popular natural and building material. All about its formation, uses and processing \u2705 Degree of water hardness \u2705 Carbon cycle.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/\" \/>\n<meta property=\"og:site_name\" content=\"Reichelt Chemietechnik Magazine\" \/>\n<meta property=\"article:published_time\" content=\"2025-12-16T15:34:43+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2026-09-02T08:23:40+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/Wissenswertes-ueber-den-Naturstoff-Kalk.jpg\" \/>\n\t<meta property=\"og:image:width\" content=\"800\" \/>\n\t<meta property=\"og:image:height\" content=\"533\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/jpeg\" \/>\n<meta name=\"author\" content=\"Sven Weber\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Sven Weber\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"10 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/\",\"url\":\"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/\",\"name\":\"Lime and Limestone: Key facts about the natural material\",\"isPartOf\":{\"@id\":\"https:\/\/www.rct-online.de\/magazin\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/#primaryimage\"},\"image\":{\"@id\":\"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/#primaryimage\"},\"thumbnailUrl\":\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/Wissenswertes-ueber-den-Naturstoff-Kalk.jpg\",\"datePublished\":\"2025-12-16T15:34:43+00:00\",\"dateModified\":\"2026-09-02T08:23:40+00:00\",\"author\":{\"@id\":\"https:\/\/www.rct-online.de\/magazin\/#\/schema\/person\/5436b1a88f13d88d14adce42e079dcd3\"},\"description\":\"Lime is a popular natural and building material. All about its formation, uses and processing \u2705 Degree of water hardness \u2705 Carbon cycle.\",\"breadcrumb\":{\"@id\":\"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/#breadcrumb\"},\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/\"]}]},{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/#primaryimage\",\"url\":\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/Wissenswertes-ueber-den-Naturstoff-Kalk.jpg\",\"contentUrl\":\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/Wissenswertes-ueber-den-Naturstoff-Kalk.jpg\",\"width\":800,\"height\":533,\"caption\":\"Verkalkter Wasserhahn \u2013 limescale-encrusted tap\"},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/www.rct-online.de\/magazin\/en\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Lime and Limestone: Key facts about the natural material\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/www.rct-online.de\/magazin\/#website\",\"url\":\"https:\/\/www.rct-online.de\/magazin\/\",\"name\":\"Reichelt Chemietechnik Magazine\",\"description\":\"\",\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\/\/www.rct-online.de\/magazin\/?s={search_term_string}\"},\"query-input\":\"required name=search_term_string\"}],\"inLanguage\":\"en-US\"},{\"@type\":\"Person\",\"@id\":\"https:\/\/www.rct-online.de\/magazin\/#\/schema\/person\/5436b1a88f13d88d14adce42e079dcd3\",\"name\":\"Sven Weber\",\"image\":{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\/\/www.rct-online.de\/magazin\/#\/schema\/person\/image\/\",\"url\":\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/Sven_Weber.jpg\",\"contentUrl\":\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/Sven_Weber.jpg\",\"caption\":\"Sven Weber\"},\"description\":\"Durch und durch Naturwissenschaftler und Musiker: Schon in der Schule waren Sven Weber die naturwissenschaftlichen F\u00e4cher die liebsten, sodass ein Chemie-Studium die einzig logische Konsequenz war. Die Begeisterung f\u00fcr diesen Fachbereich f\u00fchrte letztlich zu einem 2. Staatsexamen als Gymnasiallehrer mit den F\u00e4chern Chemie und Mathematik. Als privater Ausgleich stand und steht die Musik: Das Spielen auf verschiedenen Instrumenten in diversen musikalischen Vereinigungen. Der Ton macht die Musik \u2013 ein f\u00fcr viele Lebensbereiche geltendes Credo! Dann stimmt auch die Chemie!\",\"url\":\"https:\/\/www.rct-online.de\/magazin\/en\/author\/s-weber\/\"}]}<\/script>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"Lime and Limestone: Key facts about the natural material","description":"Lime is a popular natural and building material. All about its formation, uses and processing \u2705 Degree of water hardness \u2705 Carbon cycle.","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/","og_locale":"en_US","og_type":"article","og_title":"Lime and Limestone: Key facts about the natural material","og_description":"Lime is a popular natural and building material. All about its formation, uses and processing \u2705 Degree of water hardness \u2705 Carbon cycle.","og_url":"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/","og_site_name":"Reichelt Chemietechnik Magazine","article_published_time":"2025-12-16T15:34:43+00:00","article_modified_time":"2026-09-02T08:23:40+00:00","og_image":[{"width":800,"height":533,"url":"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/Wissenswertes-ueber-den-Naturstoff-Kalk.jpg","type":"image\/jpeg"}],"author":"Sven Weber","twitter_card":"summary_large_image","twitter_misc":{"Written by":"Sven Weber","Est. reading time":"10 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"WebPage","@id":"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/","url":"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/","name":"Lime and Limestone: Key facts about the natural material","isPartOf":{"@id":"https:\/\/www.rct-online.de\/magazin\/#website"},"primaryImageOfPage":{"@id":"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/#primaryimage"},"image":{"@id":"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/#primaryimage"},"thumbnailUrl":"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/Wissenswertes-ueber-den-Naturstoff-Kalk.jpg","datePublished":"2025-12-16T15:34:43+00:00","dateModified":"2026-09-02T08:23:40+00:00","author":{"@id":"https:\/\/www.rct-online.de\/magazin\/#\/schema\/person\/5436b1a88f13d88d14adce42e079dcd3"},"description":"Lime is a popular natural and building material. All about its formation, uses and processing \u2705 Degree of water hardness \u2705 Carbon cycle.","breadcrumb":{"@id":"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/"]}]},{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/#primaryimage","url":"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/Wissenswertes-ueber-den-Naturstoff-Kalk.jpg","contentUrl":"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2020\/12\/Wissenswertes-ueber-den-Naturstoff-Kalk.jpg","width":800,"height":533,"caption":"Verkalkter Wasserhahn \u2013 limescale-encrusted tap"},{"@type":"BreadcrumbList","@id":"https:\/\/www.rct-online.de\/magazin\/en\/lime-and-limestone-as-natural-material\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/www.rct-online.de\/magazin\/en\/"},{"@type":"ListItem","position":2,"name":"Lime and Limestone: Key facts about the natural material"}]},{"@type":"WebSite","@id":"https:\/\/www.rct-online.de\/magazin\/#website","url":"https:\/\/www.rct-online.de\/magazin\/","name":"Reichelt Chemietechnik Magazine","description":"","potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/www.rct-online.de\/magazin\/?s={search_term_string}"},"query-input":"required name=search_term_string"}],"inLanguage":"en-US"},{"@type":"Person","@id":"https:\/\/www.rct-online.de\/magazin\/#\/schema\/person\/5436b1a88f13d88d14adce42e079dcd3","name":"Sven Weber","image":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.rct-online.de\/magazin\/#\/schema\/person\/image\/","url":"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/Sven_Weber.jpg","contentUrl":"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/Sven_Weber.jpg","caption":"Sven Weber"},"description":"Durch und durch Naturwissenschaftler und Musiker: Schon in der Schule waren Sven Weber die naturwissenschaftlichen F\u00e4cher die liebsten, sodass ein Chemie-Studium die einzig logische Konsequenz war. Die Begeisterung f\u00fcr diesen Fachbereich f\u00fchrte letztlich zu einem 2. Staatsexamen als Gymnasiallehrer mit den F\u00e4chern Chemie und Mathematik. Als privater Ausgleich stand und steht die Musik: Das Spielen auf verschiedenen Instrumenten in diversen musikalischen Vereinigungen. Der Ton macht die Musik \u2013 ein f\u00fcr viele Lebensbereiche geltendes Credo! Dann stimmt auch die Chemie!","url":"https:\/\/www.rct-online.de\/magazin\/en\/author\/s-weber\/"}]}},"_links":{"self":[{"href":"https:\/\/www.rct-online.de\/magazin\/en\/wp-json\/wp\/v2\/posts\/16829"}],"collection":[{"href":"https:\/\/www.rct-online.de\/magazin\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.rct-online.de\/magazin\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.rct-online.de\/magazin\/en\/wp-json\/wp\/v2\/users\/15"}],"replies":[{"embeddable":true,"href":"https:\/\/www.rct-online.de\/magazin\/en\/wp-json\/wp\/v2\/comments?post=16829"}],"version-history":[{"count":2,"href":"https:\/\/www.rct-online.de\/magazin\/en\/wp-json\/wp\/v2\/posts\/16829\/revisions"}],"predecessor-version":[{"id":16832,"href":"https:\/\/www.rct-online.de\/magazin\/en\/wp-json\/wp\/v2\/posts\/16829\/revisions\/16832"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.rct-online.de\/magazin\/en\/wp-json\/wp\/v2\/media\/12407"}],"wp:attachment":[{"href":"https:\/\/www.rct-online.de\/magazin\/en\/wp-json\/wp\/v2\/media?parent=16829"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.rct-online.de\/magazin\/en\/wp-json\/wp\/v2\/categories?post=16829"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.rct-online.de\/magazin\/en\/wp-json\/wp\/v2\/tags?post=16829"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}