{"id":16651,"date":"2024-09-16T08:10:09","date_gmt":"2024-09-16T06:10:09","guid":{"rendered":"https:\/\/www.rct-online.de\/magazin\/?p=16651"},"modified":"2026-07-07T09:54:24","modified_gmt":"2026-07-07T07:54:24","slug":"interfacial-tension-explained","status":"publish","type":"post","link":"https:\/\/www.rct-online.de\/magazin\/en\/interfacial-tension-explained\/","title":{"rendered":"Interfacial Tension: Small Regions, Big Effects"},"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\/interfacial-tension-explained\/#What_Are_Phases\" title=\"What Are Phases?\">What Are Phases?<\/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\/interfacial-tension-explained\/#What_Is_Interfacial_Tension\" title=\"What Is Interfacial Tension?\">What Is Interfacial Tension?<\/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\/interfacial-tension-explained\/#The_Difference_Between_Surface_and_Interfacial_Tension\" title=\"The Difference Between Surface and Interfacial Tension\">The Difference Between Surface and Interfacial Tension<\/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\/interfacial-tension-explained\/#Surface_Tension_of_Water_Explained\" title=\"Surface Tension of Water Explained\">Surface Tension of Water Explained<\/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\/interfacial-tension-explained\/#Defining_Surface_Tension\" title=\"Defining Surface Tension\">Defining Surface Tension<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/www.rct-online.de\/magazin\/en\/interfacial-tension-explained\/#Measuring_Surface_and_Interfacial_Tension\" title=\"Measuring Surface and Interfacial Tension\">Measuring Surface and Interfacial Tension<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/www.rct-online.de\/magazin\/en\/interfacial-tension-explained\/#Contact_Angle_and_Wetting\" title=\"Contact Angle and Wetting\">Contact Angle and Wetting<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/www.rct-online.de\/magazin\/en\/interfacial-tension-explained\/#Surface_Tension_in_Chemistry_%E2%80%93_Applications\" title=\"Surface Tension in Chemistry \u2013 Applications\">Surface Tension in Chemistry \u2013 Applications<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/www.rct-online.de\/magazin\/en\/interfacial-tension-explained\/#Surface_Tension_of_Different_Substances\" title=\"Surface Tension of Different Substances\">Surface Tension of Different Substances<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/www.rct-online.de\/magazin\/en\/interfacial-tension-explained\/#Capillary_Forces\" title=\"Capillary Forces\">Capillary Forces<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"https:\/\/www.rct-online.de\/magazin\/en\/interfacial-tension-explained\/#Reducing_Surface_Tension\" title=\"Reducing Surface Tension\">Reducing Surface Tension<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"https:\/\/www.rct-online.de\/magazin\/en\/interfacial-tension-explained\/#Silicone_Surfactants\" title=\"Silicone Surfactants\">Silicone Surfactants<\/a><\/li><\/ul><\/nav><\/div>\n<p style=\"text-align: justify;\"><strong>Insects that can walk on water? Fabrics that let dirt and water simply bead off? Interfacial tension explains many everyday phenomena. It also matters greatly in chemistry and engineering. Where different phases meet, regions with very special properties arise.<\/strong> \u201e<strong>God made solids, but surfaces were the work of the devil. &#8220;<\/strong><strong>Physicist Wolfgang Pauli (1900 \u2013 1958) coined this line, often quoted in connection with surfaces and interfaces. A few examples show what he meant. They also reveal whether these fine domains truly deserve such a critical view.<\/strong><\/p>\n<h2><span class=\"ez-toc-section\" id=\"What_Are_Phases\"><\/span>What Are Phases?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">A phase is a uniform region of a substance with homogeneous material properties. Depending on pressure and temperature, a substance or mixture can take on different phases. We distinguish solid, liquid and gaseous phases. For H<sub>2<\/sub>O, these are ice, water and water vapour. Physical boundaries such as interfaces can separate one phase from another.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"What_Is_Interfacial_Tension\"><\/span>What Is Interfacial Tension?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">Several unusual effects occur at phase boundaries. Properties such as viscosity or thermal conductivity often change dramatically here. A distinct force also arises at these boundaries. We call this force interfacial tension.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"The_Difference_Between_Surface_and_Interfacial_Tension\"><\/span>The Difference Between Surface and Interfacial Tension<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<div class=\"box info  \"><div class=\"box-inner-block\"><i class=\"fa tie-shortcode-boxicon\"><\/i>\n\t\t\tIn everyday language, the term surface tension appears more often than interfacial tension. Yet both describe the same thing. Each reflects a substance&#8217;s tendency to keep its boundary with neighbouring phases as small as possible.\n\t\t\t<\/div><\/div>\n<p style=\"text-align: justify;\">We speak of interfacial tension for a liquid\/liquid or liquid\/solid boundary. Surface tension, by contrast, refers to a liquid\/gas or solid\/gas interface. For a solid\/gas boundary, people often use the term free surface energy instead.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Surface_Tension_of_Water_Explained\"><\/span>Surface Tension of Water Explained<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">How does the surface tension of water arise, and why is it so high? A look at the molecular level provides the answer.<\/p>\n<p style=\"text-align: justify;\">In every water molecule (H<sub>2<\/sub>O), the oxygen carries a slight negative charge. The hydrogen atoms hold a positive partial charge. This structure forms a dipole and creates a directed, electrostatic force. When these dipoles interact in water, we call the effect a hydrogen bond.<\/p>\n<p style=\"text-align: justify;\">Inside the liquid, each molecule has neighbours on all sides, so the dipoles balance out on average. Molecules right at the surface lack a neighbour above them. As a result, they feel a force pulling them into the water. This inward pull keeps the surface small and effectively &#8220;tightens&#8221; it. Surface tension is the result.<\/p>\n<figure id=\"attachment_10339\" aria-describedby=\"caption-attachment-10339\" style=\"width: 450px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-10339 size-full\" title=\"Alignment of Intermolecular Forces in a Water Droplet\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/zwischenmolekulare-kraefte1.jpg\" alt=\"Alignment of intermolecular forces in a water droplet\" width=\"450\" height=\"414\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/zwischenmolekulare-kraefte1.jpg 450w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/zwischenmolekulare-kraefte1-300x276.jpg 300w\" sizes=\"(max-width: 450px) 100vw, 450px\" \/><figcaption id=\"caption-attachment-10339\" class=\"wp-caption-text\"><center>Alignment of Intermolecular Forces in a Water Droplet<\/center><\/figcaption><\/figure>\n<p style=\"text-align: justify;\">You can see this effect when you fill a glass slightly above its rim. The water does not spill at once. Instead, it forms a small bulge. The same force lets a paper clip float on the surface. It also allows insects such as the water strider to walk on water without sinking.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Defining_Surface_Tension\"><\/span>Defining Surface Tension<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">Enlarging a liquid&#8217;s surface requires energy. This energy works against the cohesion between the molecules.<\/p>\n<div class=\"box success  \"><div class=\"box-inner-block\"><i class=\"fa tie-shortcode-boxicon\"><\/i>\n\t\t\tAccordingly, surface tension is the work needed to enlarge the surface, divided by the newly created area. The formula expresses this as \u03c3 = \u0394W\/\u0394A.\n\t\t\t<\/div><\/div>\n<p style=\"text-align: justify;\">Depending on the context, we use energy per area (joule\/m\u00b2; J\/m\u00b2) or force per length (newton\/m). Values usually appear in millijoules per square metre (mJ\/m\u00b2) or millinewtons per metre (mN\/m).<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Measuring_Surface_and_Interfacial_Tension\"><\/span>Measuring Surface and Interfacial Tension<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">Various methods and tensiometers can determine surface and interfacial tension. These instruments either analyse the interface optically or measure the acting forces.<\/p>\n<p style=\"text-align: justify;\">A ring tensiometer, for example, pulls a platinum-iridium ring out of a liquid. It measures the force on the resulting film. From this force, we can calculate the surface tension. The ring can also pass from one liquid directly into another. This yields the corresponding interfacial tension.<\/p>\n<figure id=\"attachment_10342\" aria-describedby=\"caption-attachment-10342\" style=\"width: 450px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-10342 size-full\" title=\"Platinum-Iridium Ring of a Du No\u00fcy Tensiometer Being Withdrawn from a Liquid\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/platin-iridium-ring.jpg\" alt=\"Platinum-iridium ring of a Du No\u00fcy tensiometer being withdrawn from a liquid\" width=\"450\" height=\"281\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/platin-iridium-ring.jpg 450w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/platin-iridium-ring-300x187.jpg 300w\" sizes=\"(max-width: 450px) 100vw, 450px\" \/><figcaption id=\"caption-attachment-10342\" class=\"wp-caption-text\"><center>Platinum-Iridium Ring of a Du No\u00fcy Tensiometer Being Withdrawn from a Liquid<\/center><\/figcaption><\/figure>\n<p style=\"text-align: justify;\">Similar tensiometers work with stirrups, plates or rods, depending on the application. The bubble-pressure method reads the surface tension from the internal pressure inside gas bubbles in a liquid. The pendant-drop method calculates surface tension from the shape of a hanging droplet. A further approach measures the contact angle between a droplet and a solid. This too yields the surface and interfacial tension.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Contact_Angle_and_Wetting\"><\/span>Contact Angle and Wetting<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">At a liquid\/solid interface, the contact angle can range from 0\u00b0 to 180\u00b0. The better a liquid wets the surface, the smaller its contact angle to the solid. We call a liquid wetting when the contact angle stays below 90\u00b0. Above that value, it wets the surface poorly or not at all.<\/p>\n<p style=\"text-align: justify;\">Oils and greases lower surface tension. A clean, grease-free surface therefore decides the quality of many materials. The test-ink method checks this quality using an ink of defined surface tension. If the ink wets the surface without contracting, the material&#8217;s surface tension equals or exceeds the ink&#8217;s. If the ink contracts, the material&#8217;s value lies below that of the ink.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Surface_Tension_in_Chemistry_%E2%80%93_Applications\"><\/span>Surface Tension in Chemistry \u2013 Applications<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">What does surface tension mean for practical applications? Knowing it helps predict how liquids behave on surfaces and how well they wet them. Coating technology, pharmaceutical manufacturing, <a href=\"https:\/\/www.rct-online.de\/en\/tubes-hoses\/application-fields-for-tubings\/medical-tubing\">medical technology<\/a> and <a href=\"https:\/\/www.rct-online.de\/en\/tubes-hoses\/application-fields-for-tubings\/food-hoses\">food technology<\/a> all depend on this knowledge. It safeguards their product quality. Nanotechnology uses surface-tension effects to functionalise surfaces. On metal or plastic surfaces, it also reveals the degree of contamination.<\/p>\n<div class=\"box note  \"><div class=\"box-inner-block\"><i class=\"fa tie-shortcode-boxicon\"><\/i>\n\t\t\tFunctional surfaces often exploit the lotus effect, named after the lotus flower. It lets certain surfaces clean themselves. These materials are highly hydrophobic and therefore barely wettable. On such surfaces, droplets form spheres, bead off easily and carry dirt away with them.\n\t\t\t<\/div><\/div>\n<h2><span class=\"ez-toc-section\" id=\"Surface_Tension_of_Different_Substances\"><\/span>Surface Tension of Different Substances<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">Most liquids fall between 20 and 100 mN\/m at +20 \u00b0C (68 \u00b0F). Water measures 72.8 mN\/m. Ethanol, at 22.6 mN\/m, sits relatively low by comparison. The ethanol molecule (CH<sub>3<\/sub>CH<sub>2<\/sub>OH) also forms a dipole. Its organic group, however, makes this dipole weaker than that of H<sub>2<\/sub>O. As a result, ethanol mixes better with hydrophobic substances. Pharmaceutical manufacturers therefore often use it as a solvent.<\/p>\n<figure id=\"attachment_10344\" aria-describedby=\"caption-attachment-10344\" style=\"width: 450px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-10344 size-full\" title=\"Surface Tension Allows a Needle to Float on the Water Surface\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/nadel-schwimmt-auf-wasseroberflaeche.jpg\" alt=\"Surface tension allows a needle to float on the water surface\" width=\"450\" height=\"300\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/nadel-schwimmt-auf-wasseroberflaeche.jpg 450w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/nadel-schwimmt-auf-wasseroberflaeche-300x200.jpg 300w\" sizes=\"(max-width: 450px) 100vw, 450px\" \/><figcaption id=\"caption-attachment-10344\" class=\"wp-caption-text\"><center>Surface Tension Allows a Needle to Float on the Water Surface<\/center><\/figcaption><\/figure>\n<p style=\"text-align: justify;\">Oils also lie well below water, at around 35 mN\/m. They wet surfaces easily, which suits lubricants and penetrating oils. Mercury reaches 476 mN\/m, an extremely high value for a liquid. When released, it therefore forms its familiar beads to minimise its surface. Its high surface tension also stops it from wetting the inner walls of thin capillaries. Together with its uniform thermal expansion, this made it a popular choice for older thermometers.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Capillary_Forces\"><\/span>Capillary Forces<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">Capillary forces arise in thin <a href=\"https:\/\/www.rct-online.de\/en\/tubes-hoses\/tubing-pipes-and-capillarys-made-of-metal\">tubes and capillaries<\/a> with a very large surface relative to their volume. Here, surface tension can even exceed the pull of gravity.<\/p>\n<p><a href=\"https:\/\/www.rct-online.de\/en\/tubes-hoses\/tubing-pipes-and-capillarys-made-of-metal\/titanium-and-stainless-steel-capillaries\/28810\/stainless-steel-capillary-1.4401-aisi-316\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10347 size-medium\" title=\"Stainless Steel Capillary 1.4401 (AISI 316)\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/edelstahl-kapillare-300x300.jpg\" alt=\"Stainless steel capillary 1.4401 (AISI 316)\" width=\"300\" height=\"300\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/edelstahl-kapillare-300x300.jpg 300w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/edelstahl-kapillare-150x150.jpg 150w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/edelstahl-kapillare.jpg 500w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a> <a href=\"https:\/\/www.rct-online.de\/en\/tubes-hoses\/tubing-pipes-and-capillarys-made-of-metal\/titanium-and-stainless-steel-capillaries\/28809\/stainless-steel-capillary-glass-coated\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10348 size-medium\" title=\"Stainless Steel Capillary \u2013 Glass-Coated\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/edelstahl-kapillare-glasbeschichtet-300x300.jpg\" alt=\"Stainless steel capillary \u2013 glass-coated\" width=\"300\" height=\"300\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/edelstahl-kapillare-glasbeschichtet-300x300.jpg 300w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/edelstahl-kapillare-glasbeschichtet-150x150.jpg 150w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/edelstahl-kapillare-glasbeschichtet.jpg 500w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><\/p>\n<p style=\"text-align: justify;\">A wetting liquid climbs upward against gravity. It rises until adhesion and gravity reach a balance. The thinner the capillary, the higher the liquid rises.<\/p>\n<p style=\"text-align: justify;\"><a href=\"https:\/\/www.rct-online.de\/en\/tubes-hoses\/tubings-and-pipes-made-of-rigid-plastics\">Plastics<\/a> and <a href=\"https:\/\/www.rct-online.de\/en\/tubes-hoses\/tubing-made-of-elastomers-soft-rubber\">rubbers<\/a> often show surface tensions of 20 to 50 mN\/m. <a href=\"https:\/\/www.rct-online.de\/en\/tubes-hoses\/tubings-and-pipes-made-of-rigid-plastics\/ptfe-tubing\">PTFE (polytetrafluoroethylene)<\/a> sits at the low end with 19 mN\/m. <a href=\"https:\/\/www.rct-online.de\/en\/tubes-hoses\/tubings-and-pipes-made-of-rigid-plastics\/pe-tubing\">PE (polyethylene)<\/a>, PS (polystyrene), PVC (polyvinyl chloride) and PUR (polyurethane) rank higher at 31 to 43 mN\/m.<\/p>\n<p><a href=\"https:\/\/www.rct-online.de\/en\/tubes-hoses\/tubings-and-pipes-made-of-rigid-plastics\/ptfe-tubing\/28770\/ptfe-chemical-tubing-standard\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10349 size-medium\" title=\"PTFE Chemical Tubing \u2013 Standard\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/ptfe-chemieschlauch-standard-300x300.jpg\" alt=\"PTFE chemical tubing \u2013 standard\" width=\"300\" height=\"300\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/ptfe-chemieschlauch-standard-300x300.jpg 300w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/ptfe-chemieschlauch-standard-150x150.jpg 150w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/ptfe-chemieschlauch-standard.jpg 500w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a> <a href=\"https:\/\/www.rct-online.de\/en\/tubes-hoses\/tubings-and-pipes-made-of-rigid-plastics\/peek-tubing\/28754\/peek-high-pressure-capillary-tube-solid-colour\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10350 size-medium\" title=\"PEEK High-Pressure Capillary Tubing \u2013 Solid Colour\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/peek-hochdruck-kapillarschlauch-300x300.jpg\" alt=\"PEEK high-pressure capillary tubing \u2013 solid colour\" width=\"300\" height=\"300\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/peek-hochdruck-kapillarschlauch-300x300.jpg 300w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/peek-hochdruck-kapillarschlauch-150x150.jpg 150w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/peek-hochdruck-kapillarschlauch.jpg 500w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><\/p>\n<p style=\"text-align: justify;\"><a href=\"https:\/\/www.rct-online.de\/en\/tubes-hoses\/tubing-made-of-elastomers-soft-rubber\/silicone-tubing\">Silicone<\/a> measures 24 mN\/m, natural rubber 25 mN\/m and <a href=\"https:\/\/www.rct-online.de\/magazin\/en\/butyl-rubber-properties-and-applications\/\">butyl rubber<\/a> 27 mN\/m. Glass reaches a surface energy of about 250 mN\/m, depending on its pretreatment. Metals show far higher surface energies, exceeding 1,000 mN\/m.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Reducing_Surface_Tension\"><\/span>Reducing Surface Tension<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">A high surface tension can cause problems in certain situations. During cleaning, pure water&#8217;s high surface tension wets greasy, dirty surfaces poorly. Here, an additive must lower the surface tension and raise the cleaning power.<\/p>\n<p style=\"text-align: justify;\">So what lowers the surface tension of water? Surface-active surfactants such as ordinary washing-up liquid do the job. Their amphiphilic structure gathers at the water-air interface. There, they partly displace the water molecules. This weakens the force pulling into the liquid. Water with detergent or other surfactants therefore shows a lower surface tension than pure water.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Silicone_Surfactants\"><\/span>Silicone Surfactants<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">Silicone surfactants form a group of surface-active substances. Even at low concentrations, they lower surface tension sharply. This gives them an edge over classic surfactants such as alcohol ethoxylates. Foam production, cosmetics and agriculture all value this advantage.<\/p>\n<p style=\"text-align: justify;\">They control wetting, emulsification and foam formation very efficiently. They also serve as a substitute for fluorosurfactants, which environmental rules increasingly restrict.<\/p>\n<p style=\"text-align: justify;\">Many industries need to control the surface tension of their liquids. In printing and coating, the coating solution must have a lower surface tension than the material. Otherwise, the coating contracts and beads off. <a href=\"https:\/\/www.rct-online.de\/en\/adhesives-and-lubricants\">Adhesives<\/a> face this problem especially often.<\/p>\n<p><a href=\"https:\/\/www.rct-online.de\/en\/adhesives-and-lubricants\/adhesives\/two-component-adhesives\/30377\/ptfe-adhesive-based-on-synthetic-rubber-contact-adhesive\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10351 size-medium\" title=\"PTFE Adhesive on Synthetic Rubber Base (Contact Adhesive)\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/ptfe-kleber-300x300.jpg\" alt=\"PTFE adhesive on synthetic rubber base (contact adhesive)\" width=\"300\" height=\"300\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/ptfe-kleber-300x300.jpg 300w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/ptfe-kleber-150x150.jpg 150w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/ptfe-kleber.jpg 500w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a> <a href=\"https:\/\/www.rct-online.de\/en\/adhesives-and-lubricants\/adhesives\/one-component-adhesives\/30372\/high-tech-cyanoacrylate-adhesive-plastic\/metal\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10352 size-medium\" title=\"Cyanoacrylate Adhesive \u2013 Plastic\/Metal\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/cyanacrylester-kleber-300x300.jpg\" alt=\"Cyanoacrylate adhesive \u2013 plastic\/metal\" width=\"300\" height=\"300\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/cyanacrylester-kleber-300x300.jpg 300w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/cyanacrylester-kleber-150x150.jpg 150w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2025\/09\/cyanacrylester-kleber.jpg 500w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><\/p>\n<p style=\"text-align: justify;\">Materials with low surface tension, such as rigid PTFE plastics, often need pretreatment. Manufacturers can also adjust the adhesive itself or add bonding agents. This ensures sufficient wetting and therefore strong adhesion.<\/p>\n<pre><strong>Image sources:<\/strong>\r\nFeatured image | \u00a9 stanislavi150886 \u2013 stock.adobe.com\r\nIntermolecular forces in a water droplet | \u00a9 F\u00fcsiahh, Public domain, via Wikimedia Commons\r\nPlatinum-iridium ring of a Du No\u00fcy tensiometer | \u00a9 Tibor Dubniczky, Department of Chemistry, University of Miskolc, Hungary, CC BY-SA 3.0 &lt;https:\/\/creativecommons.org\/licenses\/by-sa\/3.0&gt;, via Wikimedia Commons\r\nNeedle floating on the water surface | \u00a9 volff \u2013 stock.adobe.com<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>Insects that can walk on water? Fabrics that let dirt and water simply bead off? Interfacial tension explains many everyday phenomena. It also matters greatly in chemistry and engineering. Where different phases meet, regions with very special properties arise. \u201eGod made solids, but surfaces were the work of the devil. &#8220;Physicist Wolfgang Pauli (1900 \u2013 &hellip;<\/p>\n","protected":false},"author":10,"featured_media":13619,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3028],"tags":[],"class_list":["post-16651","post","type-post","status-publish","format-standard","has-post-thumbnail","","category-alle-beitraege-en"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v23.1 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Interfacial Tension: Small Regions, Big Effects - Reichelt Chemietechnik Magazine<\/title>\n<meta name=\"description\" content=\"Interfacial tension explained: what it is, where it occurs, and how it differs from surface tension. 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