{"id":26,"date":"2026-03-16T18:52:50","date_gmt":"2026-03-16T17:52:50","guid":{"rendered":"http:\/\/www.7virides.com\/cs\/uvod\/bezpecnost-luh\/"},"modified":"2026-03-25T11:19:30","modified_gmt":"2026-03-25T10:19:30","slug":"bezpecnost-luh","status":"publish","type":"page","link":"https:\/\/www.7virides.com\/en\/mydlo\/bezpecnost-luh\/","title":{"rendered":"Safety when working with NaOH lye: a complete guide"},"content":{"rendered":"<blockquote>\n<p><strong>TL;DR:<\/strong> Sodium hydroxide is the only dangerous ingredient in soap making. With proper use of safety goggles and gloves, working with it is safe. Main rule: always lye into water, never the other way around.<\/p>\n<\/blockquote>\n<p>Sodium hydroxide (NaOH, caustic soda) is a substance without which solid soap cannot be made using cold or hot process. It is also the only truly dangerous ingredient in the entire process. Proper handling is simple and anyone can manage it. Improper handling causes chemical burns.<\/p>\n<p>This guide will not teach you to fear lye \u2014 it will teach you to respect it. Thousands of soap makers work with NaOH every week without incidents because they follow basic rules. This page explains those rules.<\/p>\n<h2 id=\"co-je-hydroxid-sodny-a-proc-je-nebezpecny\">What is sodium hydroxide and why is it dangerous?<\/h2>\n<p>Sodium hydroxide (NaOH) is a strong base with pH ~14 in solution. It reacts with proteins \u2014 this is why it saponifies fats and also why it causes chemical burns on skin and especially on eyes. There are three key properties to know.<\/p>\n<p><strong>First danger: exothermic reaction with water.<\/strong> When dissolving NaOH in water, heat is released \u2014 the lye solution heats up to 70\u201390 \u00b0C. That is why lye is never prepared in plastic containers with low heat resistance and why a thermometer should be used. This heating is predictable \u2014 but only if you prepare lye correctly (lye into water, not the other way around).<\/p>\n<p><strong>Second danger: fumes during solution preparation.<\/strong> When mixing NaOH with water, briefly irritating fumes (hydroxide and water vapor) are released. They are not extremely dangerous but irritate mucous membranes. Work by an open window or under a range hood \u2014 simple caution avoids them.<\/p>\n<p><strong>Third danger: reactivity with aluminum, tin and zinc.<\/strong> NaOH reacts with these metals and releases flammable hydrogen gas. Therefore never use aluminum containers or spoons \u2014 only stainless steel and alkali-resistant plastics.<\/p>\n<p><strong>How NaOH damages tissue:<\/strong> Unlike acids, which cause \"dry\" burns (coagulation necrosis), strong bases cause <strong>liquefaction necrosis<\/strong> \u2014 tissue literally dissolves. This is why chemical burns from lye can appear milder than they are \u2014 pain comes with a delay while damage continues. That is why immediate and thorough rinsing is absolutely critical.<\/p>\n<h2 id=\"jake-ochranne-pomucky-potrebujete\">What protective equipment do you need?<\/h2>\n<p>Before your first soap making session, get this protective equipment \u2014 do not use lye without it.<\/p>\n<h3 id=\"ochrana-oci-povinna\">Eye protection (MANDATORY)<\/h3>\n<p><strong>Sealed safety goggles<\/strong> (chemical splash goggles) \u2014 not sunglasses, not safety glasses without side shields. Lye can splash from the side. Goggles must have a sealed frame and good sealing around the eyes. Where to buy: hardware stores, occupational safety shops, pharmacies. Price: EUR 3\u20138.<\/p>\n<p>Why goggles are the most important: lye burns on skin are treatable. Lye injury to the eye can cause permanent vision damage or blindness. This is not fear-mongering \u2014 it is pharmacological reality. One moment without goggles is not worth it.<\/p>\n<h3 id=\"ochrana-rukou\">Hand protection<\/h3>\n<p><strong>Rubber or neoprene gloves<\/strong> (not latex \u2014 latex is too thin and permeable). Ideal are household rubber gloves (yellow or pink) \u2014 available at any drugstore. Extended gloves provide better protection than short ones, protecting the lower forearm as well. Put them on comfortably before opening the lye.<\/p>\n<h3 id=\"ochrana-tela\">Body protection<\/h3>\n<p><strong>Long sleeves<\/strong> and covered legs. Synthetic fibers (polyester, nylon) are vulnerable \u2014 prefer cotton or canvas. Older clothing you don't mind ruining. Synthetics adhere to alkaline particles longer.<\/p>\n<p><strong>Apron<\/strong> \u2014 I recommend a plastic or rubber kitchen apron. Fabric can absorb the solution and prolong contact with skin. A plastic apron protects your lower body best.<\/p>\n<h3 id=\"co-mit-po-ruce\">What to have on hand<\/h3>\n<ul>\n<li>Paper towels or cloth (not fabric \u2014 it absorbs solution)<\/li>\n<li>Clean water in a container for immediate rinsing<\/li>\n<li>Phone with charged battery (within reach, without lye on hands)<\/li>\n<li>Emergency number: 155 or 112<\/li>\n<\/ul>\n<h2 id=\"jak-spravne-pripravit-louhovaci-roztok\">How to properly prepare the lye solution?<\/h2>\n<p>This is the riskiest part of soap making. But with proper procedure it is safe \u2014 the process takes just 15 minutes.<\/p>\n<h3 id=\"zakladni-pravidlo-vzdy-louh-do-vody-nikdy-voda-do-louhu\">Basic rule: ALWAYS lye into water, NEVER water into lye<\/h3>\n<p>If you pour water into a dry container with lye, localized overheating occurs \u2014 alkaline solution may splash. If you add lye into water, heat dissipates evenly. This rule can be remembered as: <strong>&#8222;lye to water, like whisky to ice&#8220; - you add solid to liquid.<\/strong><\/p>\n<h3 id=\"postup-pripravy-krok-za-krokem\">Preparation procedure step by step<\/h3>\n<p><strong>Step 1: Prepare the environment.<\/strong> Open a window or turn on the range hood. Put on goggles and gloves. Both must be on BEFORE handling lye \u2014 not when you see they are needed. Clear the workspace of anything unnecessary \u2014 while wearing goggles, not just having them nearby.<\/p>\n<p><strong>Step 2: Weigh the water.<\/strong> Weigh distilled or boiled water into a stainless steel or polypropylene (PP \u2014 marked with number 5 on the bottom) container. Glass containers work but are risky \u2014 rapid heating can cause cracking. Do not underestimate this step \u2014 the volume of water determines the resulting temperature.<\/p>\n<p><strong>Step 3: Weigh NaOH.<\/strong> Weigh NaOH in a dry container. If NaOH has absorbed moisture from air (lumps instead of beads or flakes), it is still usable \u2014 homogenize by crushing. Store NaOH in a sealed container \u2014 atmospheric moisture degrades it. Before measuring, verify the lye is dry and powdery.<\/p>\n<p><strong>Step 4: Slowly pour NaOH into water.<\/strong> Slowly pour NaOH into water while stirring continuously. Stir without interruption \u2014 do not leave. The solution will heat up, may appear cloudy and release fumes. Turn your head away from the container, breathe to the side. The process takes 2\u20133 minutes \u2014 patience is not needed here, but caution is.<\/p>\n<p><strong>Step 5: Let it cool.<\/strong> Let the lye solution cool to 35\u201345 \u00b0C (per recipe). Place in a safe location \u2014 label the container or position it so it is clear what it contains. Cooled lye solution looks like clear water \u2014 clear labeling prevents confusion. Cooling takes 30\u201345 minutes \u2014 it can be accelerated by placing the container in ice water.<\/p>\n<h2 id=\"co-delat-pri-kontaktu-s-louhem\">What to do if you come into contact with lye?<\/h2>\n<h3 id=\"kontakt-s-kuzi\">Skin contact<\/h3>\n<ol>\n<li><strong>Immediately<\/strong> rinse the affected area with cold running water.<\/li>\n<li>Rinse for at least <strong>15\u201320 minutes<\/strong> \u2014 not one or two minutes. Twenty minutes \u2014 without exception.<\/li>\n<li>Remove contaminated clothing or jewelry if it is safe to do so.<\/li>\n<li>Do not use acid (vinegar, lemon juice) to neutralize \u2014 it causes an exothermic reaction and prolongs the injury. Only water \u2014 clean, cold, running water.<\/li>\n<li>After rinsing, contact a doctor or poison control center \u2014 even small lye burns can be more serious than they appear.<\/li>\n<\/ol>\n<h3 id=\"kontakt-s-okem-nalehave\">Eye contact \u2014 URGENT<\/h3>\n<ol>\n<li><strong>Immediately<\/strong> rinse the eye with running water \u2014 stream from a shower, tap or water reservoir.<\/li>\n<li>Rinse for <strong>at least 20\u201330 minutes<\/strong> \u2014 keep the eye open, despite the pain. This is the most important thing.<\/li>\n<li>Remove contact lenses if possible without interrupting the rinsing.<\/li>\n<li><strong>Call emergency services (155) or go to the ER<\/strong> \u2014 lye eye injury is a medical emergency. Do not wait for the condition to worsen.<\/li>\n<\/ol>\n<h3 id=\"poziti\">Ingestion<\/h3>\n<ol>\n<li><strong>Do not try to induce vomiting<\/strong> \u2014 the return path of lye causes further injury to the vocal cords and esophagus.<\/li>\n<li>Give the person 200\u2013300 ml of water or milk to drink if conscious.<\/li>\n<li>Call emergency services (155) or the poison control center.<\/li>\n<\/ol>\n<h2 id=\"jak-skladovat-hydroxid-sodny-bezpecne\">How to store sodium hydroxide safely?<\/h2>\n<p>NaOH is hygroscopic \u2014 it absorbs moisture from the air and gradually degrades. Proper storage:<\/p>\n<ul>\n<li><strong>In a sealed airtight container<\/strong> (original packaging or plastic container with lid) \u2014 there should be as little air as possible<\/li>\n<li><strong>In a dry place, out of reach of children<\/strong> \u2014 outside children's bedrooms, away from curious hands<\/li>\n<li><strong>Separately from food, cosmetics and medication<\/strong> \u2014 to prevent confusion<\/li>\n<li><strong>Away from moisture, heat and direct sunlight<\/strong> \u2014 store in a cool dark room<\/li>\n<\/ul>\n<p>Label the container clearly: <strong>\"NaOH - caustic soda - DANGEROUS&#8220;<\/strong>. A colored label simplifies identification.<\/p>\n<p>Properly stored NaOH lasts for years. If it forms lumps (absorbed moisture), you can dry it in an oven at 100 \u00b0C or use it immediately \u2014 concentration does not change, but weighing lumps is less precise. Lumps can be ground in a grinder for easier weighing.<\/p>\n<h3 id=\"kde-koupit-naoh-v-cr\">Where to buy NaOH<\/h3>\n<p>Sodium hydroxide is freely available for home and industrial use. It is sold as:<\/p>\n<ul>\n<li><strong>Drain pipe cleaner<\/strong> (Drano, Dr. Max drain cleaner, Krait) \u2014 look for products containing <strong>100% NaOH<\/strong>. Avoid products with additives (enzymes, perfume, foaming agents) \u2014 these are not suitable for soap.<\/li>\n<li><strong>At pharmacies<\/strong> \u2014 sodium hydroxide in granules or flakes (Natrium hydroxydatum, NaOH) \u2014 purity guaranteed.<\/li>\n<li><strong>Soap making e-shops<\/strong> \u2014 NaOH with certified purity, suitable for cosmetic products intended for sale.<\/li>\n<\/ul>\n<p>Note: EU Regulation 2016\/1013 restricts the sale of NaOH in concentrations above 12% (solution) to consumers without registration \u2014 but <strong>solid NaOH<\/strong> (granules, flakes) is a category outside this restriction and freely sold. There is no registration requirement for purchasing solid NaOH for home soap making.<\/p>\n<h2 id=\"jak-likvidovat-zbytky-a-odpady\">How to dispose of leftovers and waste?<\/h2>\n<p><strong>Excess lye solution<\/strong> \u2014 before making: completely dilute in a large container of water and pour into the sink. Never pour concentrated lye into a sink or toilet \u2014 it damages plastic pipes. Before flushing, verify the lye is sufficiently diluted \u2014 it should be nearly invisible.<\/p>\n<p><strong>Equipment after use<\/strong> \u2014 rinse stick blender, bowls and tools with water. Fresh lye solution on containers is safe to rinse under running water. Use gloves \u2014 even after rinsing, residue can sting. Rinse twice.<\/p>\n<p><strong>NaOH leftovers<\/strong> \u2014 do not throw in regular trash. Contact your local waste collection center or ask at a pharmacy \u2014 disposal as chemical waste should not be a problem.<\/p>\n<h2 id=\"desatero-bezpecne-prace-s-louhem\">Ten rules of safe lye handling<\/h2>\n<ol>\n<li><strong>Always safety goggles<\/strong> \u2014 without exception, throughout the entire time working with lye.<\/li>\n<li><strong>Always gloves<\/strong> \u2014 rubber or neoprene, both on your hands before you open the lye.<\/li>\n<li><strong>Lye ALWAYS into water<\/strong> \u2014 never water into lye. Forget this \u2014 and you may lose your eyesight.<\/li>\n<li><strong>Work in a ventilated area<\/strong> \u2014 by a window or under a range hood, regardless of season.<\/li>\n<li><strong>Label the lye solution<\/strong> \u2014 do not confuse with water. A visible label is worth the time.<\/li>\n<li><strong>Do not use aluminum containers<\/strong> \u2014 nor containers made of tin or zinc. Stainless steel and plastics only.<\/li>\n<li><strong>Have water within reach<\/strong> \u2014 for immediate rinsing. Before you start, know where it is.<\/li>\n<li><strong>Do not leave the workspace unattended<\/strong> \u2014 once you are in the process, stay. There is no time for a bathroom break.<\/li>\n<li><strong>In case of contact: rinse for 20 minutes<\/strong> \u2014 not less. A timer helps.<\/li>\n<li><strong>Phone within reach<\/strong> \u2014 and emergency number memorized (155).<\/li>\n<\/ol>\n<h2 id=\"caste-otazky\">Frequently asked questions<\/h2>\n<p><strong>How do I know if I've been burned by lye?<\/strong> Lye causes chemical burns \u2014 slimy feeling, redness, later blisters. If unsure, rinse for 20 minutes \u2014 there is nothing to lose. A small amount is not lethal, but a large amount is dangerous.<\/p>\n<p><strong>What if I rubbed lye into my eyes?<\/strong> Immediately go to the nearest source of clean water (shower, tap). Rinse for 20\u201330 minutes without stopping, keep the eye open. Then call emergency services \u2014 do not handle it yourself, even if it seems mild.<\/p>\n<p><strong>Can I use the same blender for food and soap?<\/strong> Technically yes, if you wash it thoroughly \u2014 but I would not do it. Lye leaves a scent trace that is difficult to completely remove. Better to buy a used blender cheaply.<\/p>\n<p><strong>Is NaOH present in cured soap?<\/strong> No. After complete saponification (24\u201348 hours) there is no free lye in the soap \u2014 it all reacted with oils. Cured soap (4+ weeks) is alkaline (pH 9\u201310), but does not contain NaOH as such. The tongue test confirms it is safe.<\/p>\n<p><strong>Will anything happen if I get splashed with lye?<\/strong> Small splash \u2014 rinse and continue. Large splash \u2014 call emergency services and see a doctor. Lye is not a poison \u2014 it is a caustic. Proceed with common sense: protection, rinsing, doctor if needed.<\/p>\n<h2 id=\"viz-take\">See also<\/h2>\n<ul>\n<li><a href=\"\/en\/soap\/what-is-cold-process-soap\/\">What is cold process soap and how does it work<\/a> \u2014 introduction to soap making<\/li>\n<li><a href=\"\/en\/soap\/first-soap-recipe\/\">Your first recipe step by step<\/a> \u2014 practical guide for beginners<\/li>\n<li><a href=\"\/en\/soap\/soap-making-equipment\/\">Soap making equipment in the Czech Republic<\/a> \u2014 where to buy protective equipment and containers<\/li>\n<\/ul>","protected":false},"excerpt":{"rendered":"<p>TL;DR: Hydroxid sodn\u00fd je jedinou nebezpe\u010dnou ingredienc\u00ed v v\u00fdrob\u011b m\u00fddla. P\u0159i spr\u00e1vn\u00e9m pou\u017eit\u00ed ochrann\u00fdch br\u00fdl\u00ed a rukavic je pr\u00e1ce s [&hellip;]<\/p>\n","protected":false},"author":0,"featured_media":0,"parent":95,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"class_list":["post-26","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.7virides.com\/en\/wp-json\/wp\/v2\/pages\/26","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.7virides.com\/en\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.7virides.com\/en\/wp-json\/wp\/v2\/types\/page"}],"replies":[{"embeddable":true,"href":"https:\/\/www.7virides.com\/en\/wp-json\/wp\/v2\/comments?post=26"}],"version-history":[{"count":2,"href":"https:\/\/www.7virides.com\/en\/wp-json\/wp\/v2\/pages\/26\/revisions"}],"predecessor-version":[{"id":139,"href":"https:\/\/www.7virides.com\/en\/wp-json\/wp\/v2\/pages\/26\/revisions\/139"}],"up":[{"embeddable":true,"href":"https:\/\/www.7virides.com\/en\/wp-json\/wp\/v2\/pages\/95"}],"wp:attachment":[{"href":"https:\/\/www.7virides.com\/en\/wp-json\/wp\/v2\/media?parent=26"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}