A shampoo soap bar is a plastic free way to wash normal hair, a true cold process soap formulated with extra castor and coconut oil for a rich, cleansing lather. It is also a cosmetic product, so the moment you sell it in Great Britain it must comply with the UK Cosmetic Products Enforcement Regulations 2013 and the retained Regulation (EC) No 1223/2009, overseen by the Office for Product Safety and Standards. This guide gives you the full formulation, the method, and a clear path to selling it legally.

This recipe is part of our maker series. If you want a wider library of tested formulas across skincare, hair care and more, our 100 Beauty Formulas cosmetic formulation guide collects one hundred professional formulations in one place.

How a shampoo bar differs from a body bar

A shampoo soap bar is still cold process soap, but the oils are chosen with hair in mind. More castor and coconut oil give a bigger, cleansing lather that rinses grease from the scalp, while olive oil and a conditioning oil keep the bar from stripping the hair. It is important to know that a true shampoo bar like this is soap, which is different from a syndet bar made from synthetic detergents. Both wash hair, but they behave differently, and a soap bar has one extra step.

That step is the acid rinse. Soap is naturally alkaline, sitting at around pH nine to ten, whereas the hair cuticle prefers a slightly acidic environment. Rinsing after washing with a diluted acid, most commonly apple cider vinegar, closes and smooths the cuticle, removes any soap film, and leaves hair soft and shiny rather than waxy. This is the single most important tip for anyone switching to a shampoo soap bar.

• Plastic free. One bar replaces bottles of shampoo.
• Rich, cleansing lather. Extra castor and coconut oil clean the scalp well.
• Long lasting. A cured bar outlasts several bottles of liquid shampoo.

The acid rinse is essential. Because soap is alkaline and hair prefers a slightly acidic pH, always rinse with one tablespoon of apple cider vinegar in a cup of water after washing. This closes the hair cuticle and is the secret to soft, shiny results rather than a waxy feel.

What is saponification?

Saponification is the chemical reaction at the heart of every real soap. When oils and butters, which are triglycerides, are mixed with sodium hydroxide dissolved in water, the two react to form soap and glycerin. The important safety point is that the sodium hydroxide is used up in the reaction. A correctly made, fully cured bar contains no free lye, which is exactly why finished soap is safe and gentle to use on the skin. Understanding this also explains why measuring matters so much: too little lye leaves a soft, oily bar, while too much leaves a harsh, lye heavy one.

A safety word before you start

Cold process soap is made with sodium hydroxide, also known as lye or caustic soda. It is a corrosive alkali that can cause serious chemical burns and permanent eye damage before it is saponified, so it deserves real respect. Treat it as a hazardous substance and follow the Health and Safety Executive guidance on the control of substances hazardous to health (COSHH), along with the safety data sheet supplied with your lye. The essential rules are simple and non negotiable:

• Wear personal protective equipment. Safety goggles, chemical resistant gloves and long sleeves at all times when handling lye or raw soap.
• Work in a well ventilated space, away from children and pets, with windows open or extraction running.
• Always add lye to water, never water to lye. Adding water to lye can erupt violently. Makers remember it as snow floats on water, so you sprinkle the lye onto the water.
• Keep white vinegar nearby to neutralise surface spills, and rinse any skin contact with plenty of cool running water.
• Use dedicated soaping equipment that never touches food again, and label it clearly.

This level of care is only needed at the raw lye stage. Once your soap has saponified and cured, it is simply soap, mild and safe to use.

Equipment you will need

• A digital scale accurate to one gram, for weighing every ingredient
• A stick blender (immersion blender) to reach trace quickly
• Two heatproof jugs, one for the lye solution and one for the oils
• A stainless steel or heavy plastic mixing bowl, never aluminium, which reacts dangerously with lye
• A silicone spatula and a digital thermometer
• A silicone loaf mould or individual cavity moulds
• Safety goggles, chemical resistant gloves and an apron

Avoid aluminium and non stick coatings entirely, as lye corrodes aluminium and can release hydrogen gas. Stainless steel, silicone and heavy duty plastic are the safe choices, and keeping a dedicated set of soaping tools makes every batch cleaner and safer.

The shampoo bar formulation

This makes roughly 1.3 kilograms of soap, by weight. The oils are chosen to give a cleansing yet balanced bar for normal hair.

Higher castor for lather. Castor oil at fifteen percent gives the rich, bubbly lather that makes a shampoo bar feel genuinely cleansing on the scalp. It is the key oil in this recipe.

Verify before you make it. Run your exact recipe through a reputable lye calculator before mixing, without exception.

Balance for normal hair. This blend suits normal hair. For oilier hair you can nudge the coconut up slightly, and for drier hair raise the olive and shea a little.

Scent and allergens. Essential oils such as rosemary and peppermint suit hair and scalp, and they carry allergens that must be declared above set thresholds. Confirm your levels with an allergen compliance check.

How to make it, step by step

Allow about ninety minutes of active work, then a day or two before unmoulding.

1. Prepare

Wear goggles and gloves, keep children and pets away, and weigh everything before you begin.

2. Make the lye solution

Sprinkle the sodium hydroxide into the distilled water, stir until clear, and set aside to cool.

3. Prepare the oils

Melt the coconut oil and shea butter, then add the olive, sunflower and castor oils.

4. Combine and blend to trace

With both around forty degrees Celsius, pour the lye into the oils and blend to a light trace. Castor rich batters can thicken quickly, so watch it closely and stop at light trace.

5. Scent, mould and insulate

Blend in your essential oils, pour into the mould, tap to release air bubbles, cover and insulate with a towel overnight.

6. Unmould and cut

Unmould after one to two days and cut into bars while wearing gloves.

Curing your bar

Cure the bars for four to six weeks in a cool, dry, airy place, turning occasionally. As with all cold process soap, curing lets the bar harden and mellow, which gives a milder wash and a longer lasting bar.

How to use your shampoo bar

To wash, rub the bar between wet hands to build a lather, or stroke it directly over wet hair a few times, then massage the lather into the scalp and rinse well. Follow with the acid rinse, pouring diluted apple cider vinegar over the hair, then rinsing again with water. Allow a week or two of adjustment when you first switch, as your hair and scalp settle into soap washing, and keep using the acid rinse throughout.

Testing your soap

Two simple checks confirm your bar is safe and ready to use.

• The zap test. Touch a well cured bar briefly to the tip of your tongue. Soap tastes of soap. A sharp, battery like zap means there is unreacted lye, so the bar needs a longer cure or has a recipe error. Only zap test a bar that has cured for several weeks.
• pH. Handmade soap is naturally alkaline, usually around pH nine to ten, which is completely normal for a soap. Check with pH strips on a wet lather. A reading well above this range suggests a lye heavy batch, so recheck your measurements before selling it.

Storing and using your soap

Once cured, keep your bars somewhere cool, dry and out of direct sunlight, ideally loosely wrapped or boxed so they stay clean and firm rather than gathering dust or softening. In the shower or by the sink, a well drained soap dish that lets the bar dry fully between uses will make it last far longer, because a bar left sitting in a puddle of water softens and dissolves quickly.

Handmade soap is at its best within about a year of its cure date, although a well made, well stored bar will happily keep for longer than that. If you sell your soap, remember that its shelf life, storage conditions and the period after opening all form part of the information a safety assessment reviews, so it is worth keeping a clear note of every batch date from the start.

Labelling your soap for sale

Selling your soap means labelling it correctly, and the requirements are specific. Under Regulation (EC) No 1223/2009 and the UK cosmetic rules, a cosmetic label must carry the name and function of the product, the name and address of the Responsible Person, the country of origin where required, the nominal weight at the time of packaging, a batch number, the period after opening or a minimum durability date, any mandatory warnings, and a full ingredient list. That list must use INCI names in descending order of weight, and for a cold process soap the oils appear in their saponified form, so olive oil is listed as Sodium Olivate, coconut oil as Sodium Cocoate, shea butter as Sodium Shea Butterate, and so on, alongside water (Aqua), the naturally produced glycerin, and any fragrance allergens that sit above their declaration thresholds.

The ingredient list, the allergen declarations and the mandatory warnings are the three places small brands most often slip up, so it is well worth having a label and packaging review before you commit to a print run. A correct, professional label keeps you compliant, saves you from costly reprints, and builds real trust with the customers who take the time to read it.

Troubleshooting common problems

• Waxy or heavy hair. Almost always a missing or too weak acid rinse, or hard water. Always rinse with diluted apple cider vinegar, and use a stronger dilution in hard water areas.
• Not enough lather. Increase the coconut and castor slightly, and make sure the bar has fully cured.
• A thick, fast trace. Castor speeds trace, so soap a little cooler and pour promptly.
• Scalp feels dry. Nudge the olive and shea up a little, and do not over wash.

Variations

• Rosemary and mint. A refreshing, invigorating scalp bar, popular for a clarifying wash.
• Extra conditioning. Raise the olive and shea for a gentler bar aimed at drier hair.
• Clarifying clay bar. Add a spoon of kaolin clay for a deeper clean and extra slip.

From kitchen to shelf: selling your shampoo bar legally

Handmade shampoo bar is a cosmetic, so the moment you sell it, it must meet UK and EU cosmetic law before it goes on the market. Here is what compliance involves.

• A Cosmetic Product Safety Report. Every cosmetic sold in the UK or EU needs a Cosmetic Product Safety Report (CPSR), a formal safety assessment signed by a qualified Safety Assessor under Regulation (EC) No 1223/2009. If you make several variants, they can be assessed together as a range through our multiple variant CPSR service.
• The full document set. Alongside the CPSR you must hold a Product Information File, and your product must be notified. Our all in one compliance package covers the CPSR, PIF, SDS and notification together.
• Notification. Before sale, your product is notified in Great Britain through the Submit cosmetic product notifications service (SCPN), and in the EU through the CPNP, which we handle in our CPNP product notification service. It is declared under the correct frame formulation, a soap shampoo, so your exact recipe stays private.
• Responsible Person and labelling. Every product needs a Responsible Person who is legally accountable to the authorities, and a compliant label. Phoenix can act as your UK and EU Responsible Person and carry out a label and packaging review.
• Selling in the United States? Under the Modernization of Cosmetics Regulation Act, the US Food and Drug Administration now requires facility registration and product listing for many cosmetics, which we manage through our FDA MoCRA listing service.
• When you are ready to take your shampoo bar to market, contact Phoenix Safety Consultants and we will guide you through every step.

Frequently asked questions

Do shampoo soap bars really clean hair?

Yes. A well formulated soap bar with extra coconut and castor oil cleans hair effectively. An acid rinse afterwards keeps hair soft and shiny.

Why do I need an apple cider vinegar rinse?

Soap is alkaline and hair prefers a slightly acidic pH. A diluted vinegar rinse smooths the hair cuticle, removes soap film, and prevents a waxy feel.

Is there an adjustment period with shampoo bars?

Many people notice a short adjustment of one to two weeks as their hair moves away from conventional shampoo. Using the acid rinse consistently helps a lot.

How is a shampoo bar notified?

For notification it is declared under the soap shampoo frame formulation, so your exact recipe stays private while the notification is completed.

Do I need a CPSR to sell a shampoo bar?

Yes. A shampoo soap bar is a cosmetic, so to sell it in the UK or EU it needs a Cosmetic Product Safety Report, a PIF, a Responsible Person and a compliant label.

About the author

This article is educational. Always run your recipe through a lye calculator, follow proper safety practices, and have any product professionally assessed before selling it.