{"id":39,"date":"2026-03-16T18:52:50","date_gmt":"2026-03-16T17:52:50","guid":{"rendered":"http:\/\/www.7virides.com\/cs\/recepty\/tekute-mydlo-koh\/"},"modified":"2026-03-25T11:19:47","modified_gmt":"2026-03-25T10:19:47","slug":"tekute-mydlo-koh","status":"publish","type":"page","link":"https:\/\/www.7virides.com\/en\/recepty\/tekute-mydlo-koh\/","title":{"rendered":"Liquid soap with KOH: recipe and production guide"},"content":{"rendered":"<blockquote>\n<p><strong>TL;DR:<\/strong> Liquid soap is made from potassium hydroxide (KOH, not NaOH) using the hot process method. KOH has a 1.403\u00d7 higher SAP number than NaOH and is usually 90% pure (not 100%). The paste takes 3-5 hours to cook, then the paste is diluted with water to make the final liquid soap.<\/p>\n<\/blockquote>\n<p>Liquid soap differs from solid soap in one basic way: sodium hydroxide (NaOH) is used instead of <strong>potassium hydroxide (KOH)<\/strong>. Sodium soap salts are solid, potassium salts are soft and soluble in water - hence the liquid consistency.<\/p>\n<p>But the production process is not just \"the same, but with a different hydroxide&#8220;. Liquid soap goes through a thick paste phase, is diluted with water and requires a slower, controlled process. This page will show you the entire process step by step.<\/p>\n<h2 id=\"jak-se-lisi-koh-od-naoh-a-proc-to-zalezi\">How does KOH differ from NaOH \u2014 and why does it matter?<\/h2>\n<p>KOH produces a liquid or soft soap, while NaOH produces a solid one. The SAP number for KOH is 1.403\u00d7 higher and KOH is typically 90% purity (not 100%). These factors require recalculation and a special procedure.<\/p>\n<table>\n<thead>\n<tr>\n<th>Result<\/th>\n<th>Bar soap<\/th>\n<th>Liquid soap or paste<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>SAP number<\/td>\n<td>Lower (e.g. 0.134 for olive)<\/td>\n<td>Higher (\u00d71.403 versus NaOH)<\/td>\n<\/tr>\n<tr>\n<td>Purity<\/td>\n<td>Usually 100 %<\/td>\n<td>Usually 90% (to be recalculated!)<\/td>\n<\/tr>\n<tr>\n<td>Availability in the Czech Republic<\/td>\n<td>Easily (drugstore as a pipe cleaner)<\/td>\n<td>Worse - pharmacies, e-shops<\/td>\n<\/tr>\n<tr>\n<td>Price<\/td>\n<td>Lower<\/td>\n<td>Higher<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h3>Saponification numbers for KOH<\/h3>\n<p>The SAP values for KOH are approximately 1.403\u00d7 higher than for NaOH. Reason: molecular weight of KOH (56.1 g\/mol) vs. NaOH (40.0 g\/mol). Ratio: 56,1 \u00f7 40,0 = 1,403.<\/p>\n<p>Examples:<\/p>\n<ul>\n<li>Olive oil: NaOH SAP 0.134 \u00d7 1.403 = <strong>KOH SAP 0,188<\/strong><\/li>\n<li>Coconut oil: NaOH SAP 0.178 \u00d7 1.403 = <strong>KOH SAP 0,250<\/strong><\/li>\n<li>Castor oil: NaOH SAP 0.128 \u00d7 1.403 = <strong>KOH SAP 0,180<\/strong><\/li>\n<\/ul>\n<h3>KOH purity: critical factor<\/h3>\n<p>Commercial KOH is usually 90% pure (the remaining 10% is water and carbonates). Unlike NaOH, which is 100%, <strong>you must always convert the amount of KOH to actual purity<\/strong>:<\/p>\n<p>If the calculator says 90 g of pure KOH and you have 90% KOH: 90 \u00f7 0.90 = <strong>100 g of real KOH<\/strong> you measure on the scale.<\/p>\n<p>Always check for cleanliness on the packaging or in the supplier's technical data sheet.<\/p>\n<h2 id=\"jak-vyrobit-tekute-mydlo-hot-process-s-koh\">How to make liquid soap \u2014 hot process with KOH<\/h2>\n<p>The production is done in three stages: cooking the paste (2-3 hours in a slow cooker), testing for doneness and dilution with water. The hot process requires patience, but the control is clear - the paste goes through distinct stages.<\/p>\n<p>Liquid soap is made using the hot process method - we boil the paste until the saponification is complete, then dilute it with water.<\/p>\n<h3>Overview<\/h3>\n<table>\n<thead>\n<tr>\n<th><strong>Paste yield<\/strong><\/th>\n<th>~700 g<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td><strong>Yield of liquid soap<\/strong> (after dilution)<\/td>\n<td>1,5-2 l<\/td>\n<\/tr>\n<tr>\n<td><strong>Difficulty<\/strong><\/td>\n<td>\u2605\u2605\u2605\u2606\u2606<\/td>\n<\/tr>\n<tr>\n<td><strong>Production time<\/strong><\/td>\n<td>3-5 hours<\/td>\n<\/tr>\n<tr>\n<td><strong>Curing<\/strong><\/td>\n<td>24-48 hours after dilution<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h3>Ingredients (paste)<\/h3>\n<ul>\n<li>350 g olive oil (50 %)<\/li>\n<li>210 g coconut oil (30%)<\/li>\n<li>140 g castor oil (20 %)<\/li>\n<li>96.4 g KOH (90% purity)<\/li>\n<li>260 g distilled water<\/li>\n<\/ul>\n<p><strong>Calculation of KOH:<\/strong><\/p>\n<ul>\n<li>Olive (SAP KOH 0,188): 350 \u00d7 0,188 = 65,8 g<\/li>\n<li>Coconut (SAP KOH 0,250): 210 \u00d7 0,250 = 52,5 g<\/li>\n<li>Castor (SAP KOH 0,180): 140 \u00d7 0,180 = 25,2 g<\/li>\n<li>Total pure KOH (3% SF): 143.5 \u00d7 0.97 = 139.2 g of pure KOH<\/li>\n<li>For 90% KOH: 139,2 \u00f7 0,90 = <strong>154,7 g KOH<\/strong> weigh in<\/li>\n<\/ul>\n<p><em>(Always check the exact calculation in the calculator - set KOH mode and enter the purity.)<\/em><\/p>\n<p><strong>For diluting the liquid soap paste:<\/strong><\/p>\n<ul>\n<li>700 g finished paste<\/li>\n<li>700-1 400 g distilled water (depending on desired density)<\/li>\n<\/ul>\n<h3>Tools<\/h3>\n<ul>\n<li>Slow cooker or water bath pot<\/li>\n<li>Scales, stick blender, thermometer<\/li>\n<li>Safety goggles and gloves<\/li>\n<li>Sealable containers for liquid soap<\/li>\n<\/ul>\n<h3>Procedure \u2014 paste production<\/h3>\n<p><strong>1. Preparation of KOH solution<\/strong> Wear protective equipment. KOH reacts even more exothermically with water than NaOH - be careful. Weigh the water, slowly add KOH while stirring. Allow to cool to 40-50 \u00b0C.<\/p>\n<p><strong>2. Preparation of oils<\/strong> Melt the coconut oil, add the olive oil and castor oil. Temper to 50-60\u00b0C - liquid soap is made at higher temperatures than solid CP soap.<\/p>\n<p><strong>3. Connections and first trace<\/strong> Pour KOH solution into the oils. Stir with a stick blender. Trace comes faster than with CP - in 2-5 minutes.<\/p>\n<p><strong>4. Cooking the paste (2-3 hours)<\/strong> Move the pot to a slow cooker (LOW setting) or to a water bath (80-90 \u00b0C). Stir every 30 minutes.<\/p>\n<p>The paste goes through phases:<\/p>\n<ul>\n<li><strong>Applesauce phase:<\/strong> thick, uneven - like applesauce<\/li>\n<li><strong>Taffy phase:<\/strong> glossy, stiff, difficult to stir - like caramel<\/li>\n<li><strong>Vaseline phase:<\/strong> transparent or translucent, smooth, gel - <strong>done<\/strong><\/li>\n<\/ul>\n<p><strong>Doneness test:<\/strong> Dissolve a small sample of the paste (\u00bd teaspoon) in 30 ml of water. If the solution is clear or slightly cloudy without greasy bits - the paste is ready. If the solution is cloudy with oil droplets - keep cooking.<\/p>\n<p><strong>Phenolphthalein test:<\/strong> A drop of phenolphthalein solution on a small sample of paste should remain colorless. Red = free KOH = keep cooking.<\/p>\n<p><strong>5. Cooling of the paste<\/strong> Let the finished paste cool. Store the paste in an airtight container - it will last for 1 year or more.<\/p>\n<h3>Procedure \u2014 paste dilution<\/h3>\n<ol>\n<li>Weigh the paste into the pot. Add an equal amount of hot distilled water (80-90 \u00b0C).<\/li>\n<li>Stir slowly until the paste is completely dissolved - 15-30 minutes. Do not hurry, do not boil.<\/li>\n<li>Let stand for 24 hours - the liquid will clear and settle any impurities.<\/li>\n<li>Pass through a fine sieve.<\/li>\n<li>Adjust the density: add more water for a thinner consistency.<\/li>\n<li>Add essential oils or perfume (0.5-1% by weight of liquid soap).<\/li>\n<\/ol>\n<h3>Consistency and thickening<\/h3>\n<p>Paste liquid soap is naturally thinner than commercial liquid soap. For a thicker consistency:<\/p>\n<p><strong>Salt solution:<\/strong> Dissolve 1 teaspoon of table salt in 50 ml of water and add to the liquid soap while stirring. Test the density - too much salt will cause thinning.<\/p>\n<p><strong>Hydroxyethylcellulose (HEC):<\/strong> A natural thickener, available in cosmetics stores. 0.5-1% creates a gel-like consistency.<\/p>\n<p><strong>Xanthan gum:<\/strong> 0.3-0.5% for thick, thick liquid soap.<\/p>\n<h2 id=\"konzervace-tekuteho-mydla\">Preservation of liquid soap<\/h2>\n<p>Liquid soap has a higher pH (9-10) and resists bacteria. Yet, when water and botanical additives are added, the microbial risk increases.<\/p>\n<p><strong>No added botanical ingredients:<\/strong> Preservative is not necessary. High pH protects naturally.<\/p>\n<p><strong>With botanical ingredients (herbal extracts, aloe vera, hydrolates):<\/strong> Recommend a preservative. Suitable for home use: <strong>Optiphen<\/strong> (0.75-1.5%) or <strong>Liquid Germall Plus<\/strong> (0.1-0.5%) - both available in cosmetics e-shops.<\/p>\n<p><strong>Shelf life:<\/strong> Without preservative and botanist 6-12 months in an airtight container. With preservative 12-18 months.<\/p>\n<h2 id=\"caste-otazky\">Frequently asked questions<\/h2>\n<p><strong>What is the difference between 90% and 100% KOH and how does it affect the soap?<\/strong> KOH in the store is usually 90% pure, the remaining 10% is water and carbonates. If the calculator says 100 grams of pure KOH, measure 111 grams of commercial 90% KOH on the scale. Without recalculation, the soap will be undersaponified (cloudy).<\/p>\n<p><strong>How do I know if the paste is ready?<\/strong> A small sample of the paste is dissolved in 30 ml of cold water to form a clear solution without greasy bits. Phenolphthalein test: a drop of indicator on the paste should remain colourless (not red - this would indicate free KOH).<\/p>\n<p><strong>Pasta still cloudy in water after cooking - what to do?<\/strong> Turbidity means unsaponified oils. Keep cooking. After 4+ hours, check KOH calculation - may be too little KOH or miscalculated purity.<\/p>\n<p><strong>Liquid soap is too thin - how to thicken it?<\/strong> Add a thickener (salt solution, HEC or xanthan gum). Or use less water when diluting the paste.<\/p>\n<p><strong>What are the stages of cooking the paste and how do I know which is which?<\/strong> Applesauce (uneven, loose), Taffy (glossy, solidifies), Vaseline (translucent, gel - done). Each stage takes 30-60 minutes, progressing in succession.<\/p>\n<p><strong>How much water should I add to the paste?<\/strong> The ratio is 1:1 to paste weight for a standard fine consistency. More water = thinner soap, less water = thicker. Test gradually.<\/p>\n<p><strong>Do I need to add a preservative to liquid soap?<\/strong> Without botanical additives, no preservative is necessary - the high pH protects naturally. With herbs (aloe, hydrolates) add Optiphen (0.75-1.5%).<\/p>\n<p><strong>See also:<\/strong><\/p>\n<ul>\n<li><a href=\"\/en\/soap-making-ingredients\/soap-calculator\/\">Soap calculator<\/a> - KOH mode and cleanliness settings<\/li>\n<li><a href=\"\/en\/soap-making-ingredients\/saponification-chemistry\/\">Chemistry of saponification<\/a> - why KOH gives liquid and NaOH gives solid soap<\/li>\n<li><a href=\"\/en\/selling-handmade-soap\/eu-regulations-soap-making\/\">EU regulations<\/a> - liquid soap is subject to the same rules as solid<\/li>\n<\/ul>\n<blockquote>\n<p>\u26a0\ufe0f <strong>Recipe disclaimer<\/strong><\/p>\n<p>This recipe has been created or revised with the help of artificial intelligence tools and has undergone a recalculation of the KOH grammages. We still recommend checking the lye grammage in an independent calculator before production (e.g. <a href=\"http:\/\/soapcalc.net\" target=\"_blank\" rel=\"noopener\">SoapCalc<\/a>). Working with potassium hydroxide requires protective equipment - see <a href=\"\/en\/soap\/lye-safety-soap-making\/\">Lye safety<\/a>. Information is for educational purposes; the manufacturer is not liable for damages resulting from their use.<\/p>\n<\/blockquote>","protected":false},"excerpt":{"rendered":"<p>TL;DR: Tekut\u00e9 m\u00fddlo se vyr\u00e1b\u00ed z hydroxidu draseln\u00e9ho (KOH, nikoli NaOH) metodou hot process. KOH m\u00e1 1,403\u00d7 vy\u0161\u0161\u00ed SAP \u010d\u00edslo [&hellip;]<\/p>\n","protected":false},"author":0,"featured_media":0,"parent":15,"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-39","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.7virides.com\/en\/wp-json\/wp\/v2\/pages\/39","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=39"}],"version-history":[{"count":4,"href":"https:\/\/www.7virides.com\/en\/wp-json\/wp\/v2\/pages\/39\/revisions"}],"predecessor-version":[{"id":217,"href":"https:\/\/www.7virides.com\/en\/wp-json\/wp\/v2\/pages\/39\/revisions\/217"}],"up":[{"embeddable":true,"href":"https:\/\/www.7virides.com\/en\/wp-json\/wp\/v2\/pages\/15"}],"wp:attachment":[{"href":"https:\/\/www.7virides.com\/en\/wp-json\/wp\/v2\/media?parent=39"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}