Soap Making
Companion

1.1 Why Make Your Own Soap

Soap making is one of the most satisfying crafts you can take up at home. With a few oils, a carefully measured amount of lye and an hour of focused work, you turn kitchen ingredients into something genuinely useful, and every choice in the bar is yours: the oils, the scent, the colours, the swirls.

Unlike candle making, where wax simply melts and sets, soap making is a chemical reaction between fats and a strong alkali. That is what makes it fascinating, and it is why this guide spends real time on safety, measurement and understanding what happens in the pot. None of it is difficult, but all of it matters. The reward is a mild, long-lasting bar that keeps all the glycerine the reaction produces.

1.2 How to Use This Guide

Read Chapters 2 and 3 before you buy any lye. Chapter 2 explains the chemistry, because almost every later decision follows from it. Chapter 3 is the lye safety chapter, and it is the most important chapter in the book. Chapters 4 to 6 cover equipment, oils, fragrance, colour and recipe calculation. Chapter 7 walks through a first cold process batch, Chapter 8 covers other methods and design, and Chapter 9 is troubleshooting.

Chapter 10 covers selling soap in the UK. If you plan to sell even a few bars at a craft fair, read it carefully first. Chapter 11 covers packaging, storage and records, Chapter 12 has three case studies, and the glossary and appendix give reference tables, a lye safety card and a batch record template.

1.3 The Four Main Methods

Cold process blends oils and a lye solution until they thicken, then leaves the soap to finish reacting in the mould on its own warmth; it is where most makers start and stay. Hot process cooks the same batter until the reaction is complete before moulding. Melt and pour uses a ready-made base, so there is no lye to handle, which makes it the right starting point for children with adult supervision. Liquid soap uses potassium hydroxide and is best left until you are confident with bar soap.

You do not need a chemistry degree to make soap, but a few ideas explain why you weigh everything, why recipes cannot be scaled by eye, and why bars need to cure.

2.1 Oils and Fats Are Triglycerides

Every oil, butter and fat used in soap is made mostly of triglycerides: a small backbone of glycerol carrying three long fatty acid chains.

Each oil carries its own mixture of fatty acids. Coconut oil is rich in lauric and myristic acids, which make a hard, very cleansing, bubbly soap. Olive oil is mostly oleic acid, which gives a gentle, conditioning bar. Castor oil is mostly ricinoleic acid, which helps lather. Palm, lard, tallow, shea and cocoa butter bring palmitic and stearic acids for hardness and creamy lather. Choosing a recipe is really choosing a blend of fatty acids.

2.2 Lye: Sodium Hydroxide and Potassium Hydroxide

• Sodium hydroxide (NaOH), or caustic soda, makes hard bar soap. It is sold as beads, pearls or flakes.
• Potassium hydroxide (KOH) makes soft or liquid soap. It is usually sold as flakes, typically around 90% pure, which matters when you calculate (Section 8.4).

They are not interchangeable. Because of their molecular weights (40.00 for NaOH, 56.11 for KOH), the same oil needs more KOH than NaOH, and calculators convert between them by dividing KOH values by about 1.403.

2.3 What the Reaction Makes: Soap and Glycerine

When a triglyceride meets sodium hydroxide in water, the three fatty acid chains split off the glycerol backbone. Each pairs with sodium to become a soap molecule, and the backbone is released as glycerine. This is saponification.

Each soap molecule has a water-loving head and an oil-loving tail. The tails cling to grease and the heads keep the cluster suspended in water, so it rinses away.

Commercial makers often remove the glycerine; handmade soap keeps it, roughly a tenth of the oil weight depending on the oil. Glycerine draws moisture from the air, which is kind to skin but is also why handmade soap can “sweat” in humid rooms.

2.4 SAP Values

Each oil needs a specific amount of lye to saponify completely: its saponification (SAP) value, given as grams of lye per gram of oil. The widely used SoapCalc database gives olive oil a NaOH SAP value of 0.135 and coconut oil (76 degree) 0.183, so 100 g of olive oil needs 13.5 g of sodium hydroxide but 100 g of coconut oil needs 18.3 g.

SAP values are averages; natural oils vary by harvest and supplier. That is one reason for a superfat, and why you must never swap one oil for another without recalculating.

2.5 Superfat

A superfat is a deliberate shortfall of lye. Calculate the lye needed for every gram of oil, use 5% less, and about 5% of the oils stay unreacted in the bar. That makes the soap milder and gives a safety margin against small weighing errors and natural SAP variation.

Five per cent suits most bar soap. Liquid soap uses 0 to 3%, since free oil clouds it. Salt bars and very high coconut recipes use 15 to 20% to soften their harshness. Very high superfats in ordinary bars make them softer and quicker to go rancid.

2.6 Water and Lye Concentration

The lye is dissolved in water before it meets the oils; most of that water evaporates during the cure. Calculators let you set it three equivalent ways:

• Water as % of oils. SoapCalc's beginner default is 38%.
• Lye concentration: lye as a percentage of the lye solution. 33% is a common working figure.
• Water to lye ratio: 2:1 is the same as a 33.3% lye concentration.

More water gives more working time but slower unmoulding, more shrinkage, and more soda ash and glycerine rivers. Less water (a “water discount”) gives firmer bars sooner but faster thickening and more heat. Most recipes stay between about 25% and 40% lye concentration; SoapCalc warns that above 40% the reaction may not complete, leaving unreacted lye.

2.7 Trace

As you blend lye solution and oils, saponification begins and the batter thickens. Trace is the point at which it has emulsified and will not separate: batter drizzled across the surface leaves a visible trail before sinking back.

• Light trace, like thin custard: best for swirls.
• Medium trace, like pourable custard: good for layers.
• Thick trace, like pudding: for textured tops.

Trace means the reaction is under way, not finished. Saponification continues in the mould for a day or two, and the batter and fresh soap stay caustic until it is done.

Sodium hydroxide is classified as causing severe skin burns and eye damage (hazard statement H314) and as corrosive to metals (H290). Handled with the right habits it is perfectly manageable. Set those habits up from your first batch and never relax them.

3.1 What Lye Does and Why It Hurts

Sodium hydroxide attacks tissue. On skin it breaks down fats and proteins, so a lye burn can feel slippery at first rather than painful, and it keeps penetrating until rinsed away. In the eye it can cause serious, permanent damage within seconds. Swallowed, it damages the mouth, throat and stomach.

Lye is hazardous in three forms: dry beads or flakes, hot lye solution, and fresh soap batter, which stays caustic until saponification is complete.

3.2 Personal Protective Equipment

• Goggles, not glasses. Closed chemical splash goggles that seal around the eyes. Look for goggles marked to EN 166 with the field-of-use symbol “3” (liquid droplets). Over-spectacle goggles are available.
• Chemical-resistant gloves covering the wrists. Nitrile gloves are widely used for splash protection; SDSs list thicker neoprene or butyl rubber for longer contact. Change splashed gloves straight away.
• Long sleeves, covered legs and an apron. Splashes most often land on forearms.
• Closed shoes.
• A face shield over goggles is worth considering for large batches.

3.3 Mixing the Lye Solution Safely

• Always add the lye to the water, never the water to the lye. Water poured onto lye can heat violently in one spot, boil and spit caustic solution out of the jug.
• Use cold or room temperature distilled water. Minerals in tap water can affect the soap.
• Expect heat. Dissolving lye releases a great deal of heat, and the solution quickly becomes hot enough to scald. Hold the jug by its handle and stand it on a heatproof surface.
• Expect fumes. For the first minute or so the solution gives off steam carrying an irritating caustic mist. Do not lean over the jug. Work by an open window, under an extractor or outdoors.
• Stir gently with a stainless steel spoon or silicone spatula until the solution clears.
• Label it. Lye solution looks exactly like water. Write LYE on the jug and never leave it where anyone could pick it up or drink from it.

3.4 Containers and Tools

• No aluminium. Sodium hydroxide attacks aluminium (and zinc and tin), giving off flammable hydrogen gas.
• Good choices: stainless steel, and polypropylene (recycling code 5, PP) or high-density polyethylene (code 2) plastics.
• Avoid glass for lye solution. The heat can crack it, and lye slowly etches and weakens it.
• Keep soap equipment separate from food equipment, and mark it if it lives in the kitchen.

3.5 Storage, Children and Pets

• Keep lye in its original labelled container, lid tight, in a dry, cool place as the SDS asks. It absorbs moisture and carbon dioxide from the air if left open.
• Store it high up and out of reach of children, ideally locked away, apart from food, drink and acids. Never decant it into a food container.
• Keep children and pets out of the room for the whole lye stage, until the equipment is cleaned.
• Fresh soap and batter scraps are caustic too. Keep moulds and scraps out of reach until the soap is cut and curing.

3.6 First Aid for Lye Contact

These steps follow NHS guidance on chemical burns and the first-aid section of sodium hydroxide SDSs. Keep the lye safety card from the appendix where you work.

On the skin

1. Call 999. The NHS advises calling 999 if someone has got a chemical on their skin or in their eyes.
2. Wear gloves if you are helping someone else. Carefully remove contaminated clothing and jewellery, and brush off dry lye.
3. Put the area under cool or lukewarm running water, or pour lots of water over it, for about an hour, as the NHS advises. Do not stop because it has stopped hurting.
4. Put nothing else on the burn: no creams, and no vinegar or other chemicals.

In the eye

1. Rinse immediately with plenty of clean running water, holding the eyelids open. SDSs specify at least 15 minutes; keep going until help arrives.
2. Remove contact lenses if easy, then keep rinsing.
3. Call 999 or have someone call while you rinse.

If swallowed

Do not try to make the person sick. Rinse the mouth with water and call 999. Take the SDS with you.

3.7 Spills and Clean-Up

• Dry lye: wearing gloves and goggles, sweep it up carefully without raising dust and seal it in a labelled container. Ask your council about household hazardous waste for any you cannot use. Wipe the area with plenty of water.
• Lye solution: keep people and pets away, soak it up with old towels or paper while gloved, then wipe repeatedly with water.
• Raw batter: scrape and wipe off what you can. Batter-covered tools left for a day turn to soap that washes off easily.
• Splashed clothing: take it off straight away and rinse any skin it touched.

3.8 Neutralising Myths

You will often read that you should keep vinegar handy to “neutralise” lye on skin. Do not use vinegar, lemon juice or any acid on skin or eyes. NHS advice is plenty of running water and nothing else on the burn. Neutralising gives off heat on top of the burn, time spent on vinegar is time not spent rinsing (which is what actually removes the lye), and acid in an eye adds a second injury. Some makers wipe worktops with diluted vinegar after cleaning up with water; that is fine for a worktop and has no place in first aid.

4.1 Essential Equipment

You need surprisingly little. Buy it new or dedicate it to soap making, and keep it apart from your cooking kit.

Tare the container before each ingredient and write each weight down as you go. Use the stick blender in short pulses with the head fully submerged, stirring by hand between pulses; tilting it under the surface first releases trapped air and reduces bubbles.

4.2 Moulds

A silicone loaf mould or a wooden box lined with baking paper suits beginners. Silicone is easy to unmould from; wood insulates well, encouraging gel phase (Section 7.6). Cavity moulds look lovely but are harder to insulate evenly. Avoid anything made of aluminium.

Soap suppliers usually state the weight of oils a mould is designed for. For any other mould, fill it with water to the depth you want and weigh the water; soap batter has roughly the density of water, so a batch whose total weight (oils, lye solution and additives) is close to that figure will fill it about right.

4.3 How Oils Shape a Bar

The fatty acid profile of each oil decides the character of the bar. The broad pattern, as set out in SoapCalc's guidance:

• Lauric and myristic (coconut, palm kernel): hardness, bubbly lather, strong cleansing; too much is drying.
• Palmitic and stearic (palm, lard, tallow, cocoa butter, shea): hardness and dense, creamy lather.
• Oleic (olive, sweet almond, avocado, high oleic sunflower): gentle and conditioning, softer bar, low lather.
• Linoleic and linolenic (sunflower, hemp, linseed): silky but oxidise easily, shortening shelf life.
• Ricinoleic (castor oil only): boosts and stabilises lather.

Most good recipes combine a hard, cleansing oil, a hard, creamy fat and a soft, conditioning oil, plus a little castor. Full SAP values and profiles are in the appendix.

4.4 Olive, Coconut and Palm

Olive oil is the backbone of conditioning soap: high in oleic acid, gentle, and the sole oil in Castile soap (Section 8.5). SoapCalc suggests 25 to 50% in most recipes. Cheaper pure (refined) or pomace grades work perfectly well; pomace tends to trace faster.

Coconut oil gives hardness, cleansing and big lather, usually at 20 to 30% of the oils; above 30 to 35% it can feel drying unless you raise the superfat. Soap makers use refined “76 degree” coconut oil (named after its melting point in Fahrenheit). Fractionated coconut oil is a different product with a very different SAP value.

Palm oil gives hardness and creamy lather, at 20 to 30% in many traditional recipes. Its production has been linked with deforestation and habitat loss, so many makers avoid it or buy only certified oil from the Roundtable on Sustainable Palm Oil (RSPO). RSPO oil reaches buyers through four models: Identity Preserved (a single certified source, kept separate), Segregated (several certified sources, kept separate from uncertified oil), Mass Balance (certified and uncertified oil mixed, with certified volumes tracked) and Book and Claim (credits supporting certified growers; the oil you buy is not itself certified). Ask your supplier which applies. Lard and tallow are the closest palm-free substitutes; always recalculate when you swap.

4.5 Butters and Castor Oil

Shea butter adds a creamy, conditioning feel and some hardness, typically at 5 to 10%. Melt it completely, as partly melted shea can cause false trace and grainy spots.

Cocoa butter is very hard. Unrefined versions smell of chocolate; deodorised ones do not. SoapCalc suggests no more than 15 to 20%, as more can make bars brittle.

Castor oil is almost entirely ricinoleic acid. At 5 to 8% it gives a richer, more stable lather; above about 10% bars can turn sticky.

4.6 Sunflower, Rapeseed, Lard and Tallow

Sunflower oil is cheap but ordinary types are high in linoleic acid, which oxidises readily. Keep it to a small share, or use high oleic sunflower oil, which behaves much more like olive.

Rapeseed oil is a good British olive extender that makes a soft, conditioning bar; it contains some linolenic acid, so use it in moderation. SoapCalc lists “Canola Oil” (NaOH 0.133) and a separate “Rapeseed Oil, unrefined canola” entry at 0.125. UK cooking rapeseed oil is generally a low-erucic, canola-type oil, so the canola entry is the usual choice, but check with your supplier if unsure.

Lard (pig fat) and tallow (usually beef) were the standard soap fats for centuries. Both make hard, long-lasting, creamy bars. Buy them refined or render and strain your own, and label clearly, since some people avoid animal products.

5.1 Fragrance Oils and Essential Oils

Fragrance oils are blends of synthetic and natural aroma materials. Good suppliers test them in cold process soap and say whether they accelerate trace, discolour (vanillin turns soap tan to dark brown over a few weeks) or fade. Essential oils are natural plant extracts; remember that “natural” does not mean safe at any level, since they contain the same allergens as many fragrance oils, often at higher levels, and citrus oils fade quickly in soap.

Whichever you use, buy from a supplier who provides a Safety Data Sheet (SDS), an IFRA certificate and an allergen declaration for each oil, and read their soap notes before using a new scent.

5.2 IFRA Standards and Allergens

The International Fragrance Association (IFRA) Standards set maximum use levels for many fragrance materials, by product category. In the current scheme (the 51st Amendment) bar soap, liquid soap and other mainly rinse-off body and hand products are Category 9, and the supplier's IFRA certificate gives the maximum percentage of that fragrance in the finished product for each category.

The supplier's recommended cold process rate gives a good scent; the IFRA Category 9 maximum is a safety ceiling. Use whichever is lower, and check whether the certificate's figure is a percentage of the finished product rather than of the oils.

UK cosmetics law also requires named fragrance allergens to be listed individually on the label when present above a threshold: in Great Britain, 0.01% for rinse-off products such as soap (0.001% for leave-on). Examples include linalool, limonene, citral, geraniol, coumarin and eugenol. The supplier's allergen declaration lets you or your safety assessor work out the amount in the bar.

5.3 Colourants

Use only cosmetic grade colourants. In the UK, colourants in cosmetics must be on the permitted list in Annex IV of the UK Cosmetics Regulation, identified by Colour Index (CI) numbers. Craft paints, food colouring, crayons and candle dyes are not suitable.

Disperse powders before use: stir about a teaspoon into a tablespoon of a light liquid oil from the recipe until smooth. Undispersed colour shows as specks or streaks. Colours shift as soap cures, and gel phase brightens them, so test new colourants in a small bar.

Natural colourants

Alkanet root infused in oil gives purples; madder root, pinks; annatto, yellow to orange; activated charcoal, greys and black; cocoa and coffee, browns; paprika and turmeric, oranges and golds. Spirulina and nettle give greens that often fade to khaki. If you sell, every botanical is an ingredient that must be labelled and covered by your safety assessment, so buy from suppliers who give an INCI name and data.

5.4 Additives and Exfoliants

• Sugar or honey in small amounts boosts lather but adds heat.
• Sodium lactate, added to cooled lye solution at the supplier's rate, helps bars harden for earlier unmoulding.
• Milks scorch in hot lye; makers freeze them into cubes and add lye very slowly in an ice bath.
• Salt: a little hardens a bar; a lot makes a salt bar (Section 8.6).
• Rosemary oleoresin extract (ROE) in fresh oils helps delay rancidity.
• Exfoliants: fine oats, poppy seeds, ground loofah, pumice or fine coffee. Start with about a tablespoon per 500 g of oils, since coarse particles scratch.

Run every cold or hot process recipe through a lye calculation before making it, every time, even one copied from a book. Typing errors in published recipes are not rare, and percentages have to be turned into weights for your mould.

6.1 Using a Lye Calculator

Free online calculators such as SoapCalc (soapcalc.net), Soapee (soapee.com) and the Bramble Berry lye calculator all work the same way:

1. Choose NaOH for bar soap or KOH for liquid soap (tick the 90% option if your KOH is 90% pure, as most soap-making KOH is).
2. Enter the total weight of oils in grams.
3. Set the water as % of oils, a lye concentration or a water to lye ratio (Section 2.6).
4. Set the superfat, normally 5% for bar soap.
5. Add each oil and its percentage, totalling 100%.
6. Calculate and print the recipe, which gives exact weights of each oil, lye and water.

6.2 Worked Example: Calculating by Hand

The beginner recipe used in Chapter 7, for 1,000 g of oils at 5% superfat, with SoapCalc's NaOH SAP values:

That is a water to lye ratio of about 2.03 to 1, or water at 28.5% of the oils. At SoapCalc's beginner setting of 38% water, the water would be 380 g; the lye does not change.

Step 3 is to enter the same recipe in a calculator. It should agree within a gram; small differences come from rounding. If not, find out why before weighing anything.

6.3 Reading the Soap Quality Numbers

Calculators estimate a bar's behaviour from its combined fatty acid profile. SoapCalc's seven numbers and suggested ranges, with the values for our recipe worked out from SoapCalc's published profiles:

Treat the ranges as guide rails, not rules. SoapCalc points out that 100% olive oil Castile soap falls below several ranges, with an INS of about 105, yet it is one of the best-loved soaps there is. Use the numbers to catch a recipe that will be too soft, too drying or short of lather.

6.4 Changing a Recipe Safely

• Scaling: change the total oil weight in the calculator and keep the percentages.
• Substituting: swap the oil in the calculator and recalculate; similar oils still differ.
• Oils added at trace still react with the lye, so include them in the calculation.
• Other liquids (milk, beer, tea) can replace water by weight; their sugars add heat.
• Record every change as a new recipe version. If you sell, a changed formula needs its safety assessment updated (Section 10.3).

Read this chapter through before you start, set out everything you need, and allow an uninterrupted hour and a half with no children or pets in the room.

7.1 The Beginner Recipe

A palm-free, well-balanced, forgiving bar. The lye was calculated by hand in Section 6.2 from SoapCalc's SAP values and checked against the calculator.

Superfat: 5%. The loaf weighs roughly 1.4 kg, about eleven to thirteen bars depending on how you cut. Leave it unscented the first time; if you do add fragrance, use the supplier's cold process rate, never above the IFRA Category 9 maximum on its certificate, and add it at light trace.

7.2 Preparing Your Workspace

1. Clear and cover a stable worktop near a cold tap and a window.
2. Put children and pets in another room and close the door.
3. Line the mould if needed, and have a towel or box ready for insulating.
4. Set out scales, lye jug, mixing pan, stick blender, spatulas, thermometer and distilled water.
5. Put on goggles, gloves, long sleeves and apron now, before opening anything.
6. Start a batch record sheet (see the appendix) with the date, batch number and recipe.

7.3 Making the Lye Solution

1. Tare the lye jug and weigh 285 g of distilled water.
2. Tare a separate dry container and weigh 140 g of sodium hydroxide. Close the lye container straight away.
3. At your ventilated spot, slowly pour the lye into the water, stirring gently, face turned away from the fumes.
4. Stir until clear. It will be very hot. Label the jug and leave it to cool where it cannot be knocked over or mistaken for water.

7.4 Melting the Oils and Combining

1. Weigh the coconut oil and shea butter into your pan and melt them gently on a low heat. Take them off the heat as soon as they are clear.
2. Weigh in the olive and castor oils, which bring the temperature down.
3. Check temperatures. There is no single correct figure: published recommendations run from about 32 to 43°C up to around 49 to 54°C. For a first batch, aim for oils and lye solution both around 35 to 45°C and within about ten degrees of each other, with the oils completely liquid.
4. Rest the stick blender in the oils, tilt it to release trapped air, and pour the lye solution down the blender shaft to limit splashing.

7.5 Blending to Trace

1. Stir with the blender switched off for a few seconds.
2. Pulse for three to five seconds, then stir by hand with the blender off. Repeat.
3. Within a few minutes the batter turns opaque and thickens. When a drizzle from the blender (switched off) leaves a faint trail on the surface, you have light trace.
4. For a first batch, go on to a light-to-medium trace, like thin custard. Stir in any fragrance or colour by hand now, with one or two short pulses.

7.6 Pouring, Insulating and Gel Phase

Pour into the mould, scrape out the pan, tap the mould to settle bubbles, and smooth or texture the top.

Saponification generates heat, and many batches go through gel phase: the centre warms, darkens and turns translucent like petroleum jelly, then returns to opaque over the following hours. It is normal and harmless.

• To encourage gel (brighter colours, slightly glossier bars that firm up sooner), cover the mould with card and wrap it in a towel.
• To prevent gel (often wanted for milk and honey soaps, which can scorch), leave it uncovered in a cool room or put it in the fridge for the first day.
• Partial gel, a darker ring in the middle of each bar, is purely cosmetic.

7.7 Unmoulding and Cutting

Unmould when the soap is firm enough to handle without denting, usually after 24 to 48 hours; high-olive and high-water recipes take longer. If it sticks, wait another day or freeze the mould for an hour and unmould at once.

Wear gloves: fresh soap may still contain some unreacted lye. Cut with a large knife, dough scraper or wire cutter, using a guide for even bars. If the soap drags, it is too soft; wait a day. If it crumbles, cut sooner next time.

7.8 Curing

Stand the bars on a rack in a cool, dry, airy room out of direct sunlight, with gaps between them, and turn them weekly. Leave them for four to six weeks before use.

Saponification is largely complete within a day or two, so why wait? Curing is mainly about water. As the bar loses the water from the lye solution it firms up into a harder, milder, longer-lasting bar that lathers better. Castile and other high olive recipes benefit from a much longer cure, often six months or more.

7.9 Is It Safe? Zap Testing and pH

After the cure you want to know the bar is not lye-heavy. None of the usual checks is perfect.

• Zap test. Touch the tip of the tongue to a wetted, fully cured bar. A lye-heavy bar gives a sharp tingle like licking a battery; a good bar just tastes soapy. It is quick and sensitive but subjective, and never appropriate for a bar you already suspect, such as one with visible lye pockets. Rinse your mouth afterwards.
• pH strips and meters. All true soap is alkaline; well-made bar soap is commonly reported at around pH 9 to 10, so a reading cannot easily separate a good bar from a slightly lye-heavy one. Strips are hard to read precisely in that range. A calibrated meter on a standard dilution in distilled water is consistent enough to compare batches, but still measures alkalinity rather than leftover lye.
• Phenolphthalein turns pink from about pH 8.2, so it turns pink on every soap and tells you little.

8.1 Hot Process

Hot process uses exactly the same calculation as cold process, but the batter is cooked after trace so saponification finishes before moulding.

1. Combine lye solution and oils in a slow cooker kept for soap, set to low, and blend to medium trace.
2. Cover and cook, stirring every 10 to 15 minutes and folding the edges in. The batter may separate at the edges, rise and turn waxy as it goes.
3. When the whole mass looks like translucent mashed potato or petroleum jelly with no opaque patches, it is done. Go by appearance, not the clock.
4. Stir in fragrance and colour, then press it firmly into the mould and bang out air pockets. Unmould when cool, usually the next day.

The bars can be used sooner than cold process, but a few weeks' cure still makes them harder and longer-lasting.

8.2 Melt and Pour

Melt and pour is the gentlest introduction to the craft and the best way to make soap with children, because the base is already soap.

1. Cube the base and melt it gently in short microwave bursts, stirring between each, or over simmering water. Do not let it boil; SoapCalc suggests staying below about 60 to 71°C, and your base supplier may give a narrower figure.
2. Stir in colour, let it cool a little, then add fragrance at the supplier's rate (within its IFRA Category 9 limit).
3. Pour into silicone moulds and spritz with isopropyl alcohol to pop bubbles.
4. Leave a few hours to set, unmould, and wrap straight away in cling film: high-glycerine bases sweat in humid air.

With children

• An adult melts and pours; children choose colours and scents, add embeds and decorate.
• Let the base cool to a safe working temperature before small hands are near it.
• Use cosmetic grade colourants and ask your supplier which scents suit children's products.
• Isopropyl alcohol is highly flammable and irritates the eyes. The adult keeps the spray bottle, away from any hob or flame.

8.3 Rebatching

Rebatching means grating finished soap, melting it with a little liquid and remoulding it. It rescues ugly or crumbly batches and lets you add delicate ingredients. Grate the soap (gloves on if it is fresh), heat it gently in a slow cooker or over simmering water with a few tablespoons of distilled water per 500 g, stirring until it is a sticky, lumpy paste, then press it into a mould and cure for a few weeks.

Rebatching can correct a slightly lye-heavy batch by adding a calculated amount of oil, but only if you know exactly what went wrong. If you do not, discard it (Section 9.4).

8.4 Liquid Soap with Potassium Hydroxide

Liquid soap uses KOH, is made as a paste and then diluted. Use KOH SAP values, and correct for purity if your KOH is 90%. For 500 g of oils at 3% superfat:

A calculator's 90% KOH option does this correction for you; do not apply it twice.

1. Dissolve the KOH in water exactly as for sodium hydroxide: lye into water, ventilated, goggles and gloves on.
2. Blend with the warm oils. KOH soap does not trace like bar soap; it separates, thickens and becomes a stiff, translucent paste. Keep going.
3. Cook the paste on low until a small sample dissolves clear in hot water.
4. Dilute with distilled water as your recipe directs, leave it to dissolve (usually overnight), adjust the consistency, then let it settle for a week or so before bottling.

8.5 Castile Soap

Castile soap is traditionally pure olive oil soap, named after the Castile region of Spain. For 1,000 g of olive oil at 5% superfat:

It traces slowly (do not over-blend in frustration), stays soft in the mould for several days, and needs a long cure: SoapCalc notes it becomes a hard, mild bar if you wait six months or more. The lather is low and slippery.

8.6 Salt Bars

Salt bars hold a large amount of fine salt, giving a hard, smooth bar with creamy, low lather. Salt suppresses lather, so they use lots of coconut oil, and a high superfat to offset coconut's harshness. For 500 g of oils:

Stir the salt in at light trace and pour quickly. Salt bars set fast; cut them within hours, while firm but not rock hard, or they crumble. Cavity moulds avoid the problem. Avoid coarse salt, which scratches.

8.7 Shampoo Bars: Soap Versus Syndet

• Soap-based shampoo bars are cold or hot process soap formulated for hair. Being true soap they are alkaline, and in hard water soap forms insoluble scum with calcium and magnesium, which can leave hair waxy, dull or tangled. Many users follow with an acidic rinse such as diluted vinegar. Some people love them; many find they do not suit their hair or water.
• Syndet bars (“synthetic detergent”) are not soap. They are made from mild synthetic surfactants such as sodium cocoyl isethionate, can be formulated close to the pH of hair and skin, and do not form soap scum. Most commercial shampoo bars are syndets. They need no lye but are a separate discipline with their own ingredients and hazards.

Either kind sold as a shampoo is a cosmetic needing its own safety assessment, and any hair claims must be supported (Section 10.7).

8.8 Design: Layers and Swirls

Plan colours before you mix the lye, disperse colourants in oil first, and use a slow-tracing recipe and fragrance, kept at the cooler end of your range, to buy working time.

• Layers: divide and colour the batch at light trace, pour the first layer and let it firm slightly, then pour the next gently over the back of a spatula so it spreads rather than plunging through.
• In-the-pot swirl: pour coloured batter back into the main pot in a few places, stir once, and pour.
• Drop swirl: pour colours from a height in lines along the mould.
• Hanger swirl: pour layers, then loop a bent wire tool through the loaf.
• Top swirl: drizzle colours on the surface and drag a skewer through them.

8.9 Design: Embeds, Textures and Tops

• Embeds are pieces of soap set into a fresh batch: cubes, shavings, rolled noodles or moulded shapes. Melt and pour embeds can warp if the loaf gets very hot during gel.
• Textured tops: let the top thicken slightly, lift it into peaks with a spoon, and sprinkle with mica, poppy seeds or dried calendula petals, which keep their colour better than most flowers.
• Botanicals inside the bar, such as lavender buds, usually turn brown. Put them on top or accept the flecks.
• Exfoliating layers: add oats or ground loofah to one layer for a bar with a scrubby side.

Work out whether the problem started at the pot, in the mould or during the cure, then look below. Your batch record is your best diagnostic tool.

9.1 At the Pot

9.2 In the Mould

9.3 During Cure and Storage

9.4 Lye Pockets and Lye-Heavy Soap

Lye pockets are cavities or white, crystalline or wet spots inside a bar, from undissolved lye, poor mixing or separated lye solution. Lye-heavy soap generally comes from a weighing or calculation error, an omitted oil, or the wrong oil chosen in the calculator.

• Find the cause in your batch record. If you know exactly what went wrong (for example, the castor oil was never added), you can calculate the shortfall and rebatch with the missing oil.
• If you cannot identify the cause, do not try to rescue it. A guess can leave it still lye-heavy.
• Disposal: wrap and label it, keep it from children and pets, and ask your council about household chemical waste.
• Prevention: dissolve lye fully, blend to true trace, double-check weights, and always use a calculator.

Soap is a cosmetic product in law. Selling even a handful of bars at a school fair brings you under the same cosmetics regime as a large manufacturer. Many small UK businesses sell handmade soap legally, but the rules must be met before the first bar changes hands. This chapter covers Great Britain, then the differences in Northern Ireland.

10.1 Own Use, Gifts and Placing on the Market

In Great Britain, cosmetics are governed by Regulation (EC) No 1223/2009 on cosmetic products as it was retained in UK law after Brexit and amended, chiefly by the Product Safety and Metrology etc. (Amendment etc.) (EU Exit) Regulations 2019. It is enforced through the Cosmetic Products Enforcement Regulations 2013. People usually call this the UK Cosmetics Regulation. Soap is explicitly a cosmetic: “toilet soaps” appear in the illustrative list of cosmetic products, and GOV.UK lists soaps among common cosmetic types.

The key definitions are in Article 2. Making available on the market means any supply of a cosmetic product for distribution, consumption or use on the market of Great Britain in the course of a commercial activity, whether in return for payment or free of charge. Placing on the market means the first time a particular product is made available.

What that means in practice:

• Soap you make for yourself and your household is not supplied on the market at all.
• Personal gifts to friends and family, made as a hobby with no business behind them, are not supplied in the course of a commercial activity, so the rules on safety reports, notification and labelling do not apply in the same way. You still owe them a safe product.
• Selling, whether online, at craft fairs, through a shop or to friends for money, is making available on the market. All the requirements in this chapter apply from the first sale.
• Free samples, giveaways and prizes handed out by a business are still supplied in the course of a commercial activity. GOV.UK guidance states plainly that free samples are covered and must comply with all the requirements.
• Charity stalls and fundraisers are a grey area that depends on the facts. If you are making soap to sell, even for a good cause, assume the rules apply and check with Trading Standards.

10.2 The Responsible Person

Every cosmetic product made available in Great Britain must have a Responsible Person (RP) established in the UK (Article 4). For a small UK maker selling their own soap under their own name, that is normally you, as the manufacturer. A Responsible Person can be an individual or sole trader as well as a company, and other businesses can be appointed in writing to take on the role.

The Responsible Person's address must be a real UK address where the product information is held; GOV.UK guidance says that mail forwarding addresses and PO boxes are not acceptable. The RP's duties include:

• making sure each product is safe and has a safety assessment before sale
• keeping an up-to-date Product Information File (PIF) for each product
• making sure the product is manufactured to good manufacturing practice
• notifying the product to OPSS before it is placed on the market
• making sure labelling is correct and any claims can be proved
• reporting serious undesirable effects (SUEs) to OPSS; GB guidance treats “without delay” as within 30 calendar days of anyone in the business learning of a possible SUE
• taking corrective action, withdrawal or recall if a product turns out not to comply

10.3 The Safety Assessment (CPSR) and Product Information File

Before a cosmetic product is made available, it must undergo a safety assessment, recorded in a Cosmetic Product Safety Report (CPSR) (Article 10 and Annex I). The CPSR has two parts:

• Part A, safety information, provided by the Responsible Person: the full formula, physical and chemical properties, stability, microbiological quality, impurities, packaging, intended use, exposure and ingredient toxicology. For soap that means your exact recipe and supplier documents for every ingredient, including the IFRA certificate and allergen data for any fragrance.
• Part B, safety assessment, the assessor's conclusions: whether the product is safe, any warnings or instructions for use that must appear on the label, the reasoning, and the assessor's name, address, qualifications and signature.

The assessor must hold a university qualification in pharmacy, toxicology, medicine or a similar discipline (or one recognised as equivalent). It is the Responsible Person's job to make sure the assessor is suitably qualified. Many small makers use independent assessors who specialise in handmade cosmetics; prices vary, so get quotes and ask what is included. Some will assess a base recipe with a range of approved fragrance and colour variants, but each variant must genuinely be covered.

The CPSR sits inside the Product Information File (PIF), which also holds a description of the product, details of the method of manufacture and how good manufacturing practice is followed, and evidence for any claims. The PIF must be kept in English, be readily available to Trading Standards at the address you notify, and be kept for 10 years after the last batch of the product was made available.

10.4 Good Manufacturing Practice

Cosmetic products must be manufactured in line with good manufacturing practice (GMP) (Article 8). Compliance with the designated standard ISO 22716 is the recognised way of showing this, though GOV.UK notes it is not the only way. For a small home producer, GMP in practice means:

• a clean, tidy, well-maintained work area where raw materials and products cannot get mixed up or contaminated, and where pets, food preparation and soap making do not overlap
• clean, maintained equipment kept for soap making
• known, traceable suppliers for every raw material, with their batch numbers recorded
• written methods, so each batch is made the same way
• a batch number on every product, traceable back to a full batch record
• storage that protects raw materials and finished stock
• records of complaints and what you did about them, and of any change to the process
• knowing your waste streams and disposing of them safely

The Cosmetic, Toiletry and Perfumery Association (CTPA) publishes a practical GMP guide, and the Guild of Craft Soap and Toiletry Makers, which GOV.UK lists as a contact in its guidance, supports small makers.

10.5 Notifying Through SCPN

Before a cosmetic product is placed on the market in Great Britain, the Responsible Person must notify it to the Secretary of State electronically (Article 13). This is done through the GOV.UK Submit cosmetic product notifications (SCPN) service. You will need:

• the product's name and category
• the Responsible Person's name and the address where the PIF is kept
• contact details for a named person for urgent enquiries
• details of any nanomaterials and of any substances classified as carcinogenic, mutagenic or toxic to reproduction (CMR)
• the frame formulation or composition details the service asks for, so poison centres can advise on treatment
• an image of the label and a photograph of the packaging

If anything in the notification changes, you must update it without delay. SCPN search is not public; notifications are used by Trading Standards and the National Poisons Information Service.

10.6 Labelling

Article 19 sets out what must appear on a cosmetic's container and packaging, in indelible, easily legible and visible lettering. The information must be in English. For a bar of soap, that is:

• The name and address of the Responsible Person. For imported products, the country of origin.
• The nominal content by weight, at the time of packaging (not required for packs under 5 g, free samples and single-application packs).
• A durability marking. If the product's minimum durability is 30 months or less, a “best before the end of” date (or the hourglass symbol) with the month and year. If it is more than 30 months, a period after opening (PAO) symbol (the open jar with a number of months) where relevant. Your safety assessor will advise which applies to your soap.
• Precautions for use, including any required by the Annexes and any your safety assessor specifies.
• A batch number or other reference that identifies the batch.
• The function of the product, unless it is clear from its presentation.
• A list of ingredients, headed “Ingredients”.

The ingredient list

• Ingredients are listed in descending order of weight at the time they are added; those under 1% may follow in any order.
• Use the common ingredient names (INCI names). For example olive oil is Olea Europaea Fruit Oil, water is Aqua, sodium hydroxide is Sodium Hydroxide and glycerine is Glycerin. Where INCI and other names differ, UK guidance accepts the alternative in brackets, such as Aqua (Water).
• Soap makers use two conventions: listing what goes into the pot (the oils, water and sodium hydroxide) or listing what comes out (saponified oils such as Sodium Olivate, Sodium Cocoate, Sodium Shea Butterate and Sodium Castorate, plus Aqua, Glycerin and the unreacted superfat oils). Agree the approach with your safety assessor and use it consistently.
• Fragrance is listed as Parfum. Named allergens in the GB Annex III list must also be listed individually if present above 0.01% in a rinse-off product.
• Colourants may be listed in any order after the other ingredients, using their CI numbers.

Space-saving rules for soap

Where it is impossible for practical reasons to put the ingredients or precautions on the product, they can go on an attached or enclosed leaflet, label, tag, tape or card, with the “hand in book” symbol on the packaging pointing to it. Article 19(3) adds a specific concession for soap, bath balls and other small products: where even a label, tag or leaflet is impossible for practical reasons, the ingredients can appear on a notice in immediate proximity to the container in which the product is displayed for sale. Products that are not pre-packaged, or are packed at the point of sale, follow regulation 5 of the Cosmetic Products Enforcement Regulations 2013; ask Trading Standards how to present the information for unwrapped bars on a stall.

10.7 Claims

Any claim you make about your soap, on the label, on a website, on social media or at a stall, must not imply that the product has characteristics or functions it does not have (Article 20), and must meet the common criteria for cosmetic claims: legal compliance, truthfulness, evidence support, honesty, fairness and informed decision-making.

• Avoid medicinal claims. Saying a soap treats, cures or prevents eczema, psoriasis, acne or infections makes it sound like a medicine, which is a different and much stricter legal regime.
• “Natural”, “chemical-free” and “suitable for sensitive skin” are claims too. “Chemical-free” is untrue for any soap; “sensitive skin” needs evidence.
• You can only claim “not tested on animals” if neither you nor your suppliers carried out or commissioned animal tests on the product or its ingredients for cosmetic purposes; GB guidance warns against misleading claims of this kind.
• Keep the evidence for every claim in your PIF.

10.8 Northern Ireland

Northern Ireland follows different rules. Under the Windsor Framework, the EU Cosmetics Regulation (EC) No 1223/2009, as it currently stands in EU law, applies to cosmetics placed on the Northern Ireland market. GOV.UK's statutory guidance for Northern Ireland explains the main differences:

• The Responsible Person must be established in Northern Ireland or the EU; a Responsible Person based in Great Britain cannot fulfil the role for the NI market.
• Products are notified through the EU's Cosmetic Products Notification Portal (CPNP), not SCPN.
• Products made in Great Britain and placed on the NI market are treated as imported and must show the country of origin, for example “Made in UK”.
• EU changes apply in NI, including the extended list of fragrance allergens being phased in under Regulation (EU) 2023/1545.
• A product placed on both markets needs a Responsible Person and notification for each (SCPN for GB, CPNP for NI).

Separate provisions on “qualifying Northern Ireland goods” can ease selling NI-made products into Great Britain. If you are based in or selling into Northern Ireland, read the GOV.UK statutory guidance for Northern Ireland.

10.9 Insurance, Weights and Other Law

Insurance

Product liability insurance is not a legal requirement for a sole trader with no employees, but it is strongly advisable. Under Part I of the Consumer Protection Act 1987, producers can be liable for damage caused by a defective product without the injured person having to prove negligence. Many craft fairs and markets require stallholders to hold public liability cover, and specialist insurers offer combined public and product liability policies for handmade cosmetics. Expect an insurer to ask whether your products have a safety assessment. If you employ anyone, employers' liability insurance is compulsory.

Weights

The nominal weight on your label must be honest. GB guidance on the cosmetics rules points out that the Weights and Measures (Packaged Goods) Regulations 2006 must also be complied with. They apply to packages from 5 g to 25 kg and use the “average quantity” system: on average the packs in a batch must contain at least the stated quantity, only a small proportion may fall short by more than the tolerable negative error, and none may be short by more than twice that figure. Weigh your bars after the cure, declare a weight the batch actually meets, and keep records of your checks. Handmade bars vary, so declare conservatively.

Tax and registration

HMRC's trading allowance means you may not need to tell HMRC about gross trading income of up to £1,000 a tax year, although there are exceptions; above that you will normally need to register for Self Assessment. Check GOV.UK for your circumstances.

10.10 A Pre-Launch Checklist

1. Finalise and fix your recipe, including exact fragrance and colourant percentages.
2. Gather supplier documents for every ingredient: specifications, SDSs, IFRA certificates and allergen declarations.
3. Commission a safety assessment (CPSR) from a suitably qualified assessor.
4. Build your Product Information File, including your GMP procedures and batch record system.
5. Design labels that meet Article 19 and include any warnings from the CPSR. Have the assessor check them if they offer that.
6. Notify each product on SCPN (and CPNP if selling into Northern Ireland) before it goes on sale.
7. Arrange insurance.
8. Set up batch weighing and record keeping for every batch you make.
9. Know how you would handle a complaint, a reaction report or a recall.

11.1 Packaging

Most makers wrap cold process soap in paper, card or cigar bands that let it breathe; sealing a bar that is still losing water can trap moisture.

• Card boxes and paper wraps look good, give space for labels, and suit cured cold process soap.
• Shrink wrap or cling film is best for melt and pour, which sweats in humid air, and for bars with delicate tops.
• Unwrapped bars at a stall need the required information presented next to them (Section 10.6), and should be protected from handling.
• Choose packaging that does not react with soap or absorb fragrance oils; some inks and plastics are marked or softened by fragrance. Test first.
• If you sell, your safety assessor considers the packaging too.

11.2 Storage and Shelf Life

Store finished soap somewhere cool, dry, dark and airy, away from direct sunlight and radiators. Keep different scents apart, or the fragrances will mingle. Stack bars with air between them rather than in sealed plastic tubs.

Well-made cold process soap does not go off quickly in the way a cream can, because it contains little free water and is strongly alkaline. Its useful life is usually limited by the free oils slowly oxidising, which shows as orange spots and a rancid smell, and by fragrance fading. The more polyunsaturated oils and the higher the superfat, the shorter the shelf life.

If you sell, do not guess a shelf life. Your safety assessor considers stability and decides whether the label needs a best before date or a period after opening symbol, and what figure to use.

11.3 Batch Records

A batch record captures everything about one batch. It is how you learn from each batch, and if you sell it is a core part of good manufacturing practice.

Record, for every batch:

• batch number and date
• recipe name and version, with the total oil weight, superfat and water setting
• each ingredient's actual weight used, supplier and supplier batch or lot number
• lye solution and oil temperatures when combined
• time to trace and trace level reached
• fragrance and colourant used, with amounts
• mould, insulation and whether the batch gelled
• unmoulding and cutting date, number of bars, and any problems
• cure start and finish dates, and bar weights during cure
• any test results (zap test, pH) and final appearance
• for sold batches, where the bars went (for traceability)

A blank template is in the appendix. Give each batch a simple, unique number such as year plus a running count (for example 26-014), and print that number on every label from that batch.

Three worked examples, each based on the recipes and methods in this book. They are illustrative composites rather than accounts of particular people, written to show the decisions and the reasoning at each step.

12.1 A First 1 kg Cold Process Batch

12.2 Rescuing a Seized Batch

12.3 A Beginner Melt and Pour Gift Set

A. SAP Values and Fatty Acid Profiles

Source: SoapCalc oil database (soapcalc.net, oil list and calculator data), accessed October 2026. The NaOH figures are SoapCalc's KOH values divided by 1.403, rounded to three decimal places. Fatty acid percentages are SoapCalc's typical values; real oils vary by origin and batch, which is one reason for a superfat. Always confirm with your calculator before making a batch.

B. Oil Properties at a Glance

Typical usage ranges are those suggested in SoapCalc's guidance. They are starting points for balanced bars, not legal or safety limits.

C. Lye Safety Card

D. Batch Record Template

Copy or print one sheet per batch, and keep them in date order. If you sell, these records form part of your Product Information File.

E. Key Formulas