This is a recipe developed for oily hair, specifically for scalps that produce excess sebum and benefit from a stronger clarifying action than a standard syndet bar provides. It uses two clays alongside the surfactant base to boost oil absorption, and rosemary essential oil for both scent and its well-documented scalp-stimulating properties.

I made and tested two bars before writing this. What follows is the recipe as it stands after that testing, along with honest notes on what it does, what it feels like, and where the research ends and the anecdote begins.

If you are new to making syndet shampoo bars and want to understand the base ingredients before starting, the beginner syndet shampoo bar guide covers the fundamentals. This recipe assumes familiarity with the process.

The recipe

This formula produces bars of approximately 100g each. The one-bar column is useful for a first test batch; scale to five bars once you are happy with the result.

Ingredient	1 bar (100g)	5 bars (500g)	%
SCI (sodium cocoyl isethionate)	65g	325g	65%
CAPB (cocamidopropyl betaine)	15g	75g	15%
Cetyl alcohol	10g	50g	10%
Kaolin clay	3.6g	18g	3.6%
French green clay	2.6g	13g	2.6%
Jojoba oil	2.4g	12g	2.4%
Glycerine	1g	5g	1%
Rosemary EO (non-camphor CT)	1g	5g	1%
Total	100.6g	503g	~100%

A note on the rosemary essential oil: this recipe uses the non-camphor chemotype specifically. Rosemary essential oil is available in several chemotypes — the camphor CT has a sharper, more medicinal scent and higher camphor content which can be irritating on the scalp. The non-camphor CT (typically the 1,8-cineole or verbenone CT) is better suited to a rinse-off product. Make sure you know which chemotype you have before using it. If the label does not specify, ask your supplier. Read more about essential oils in shampoo bars.

Why two clays?

There is a reason this recipe uses both kaolin and French green clay rather than doubling up on one. They are not interchangeable, they have different structures, different levels of absorbency, and different effects on the scalp.

Kaolin is a gentle, low-absorbency clay. It sits at the mild end of the cosmetic clay spectrum, which is why it appears in formulas for dry and sensitive skin as well as oily. In a shampoo bar it contributes slip, a light mattifying effect, and some cleansing assistance without risking over-drying.

French green clay is a different material. It is an illite clay, meaning it has a three-layer silicate structure that gives it considerably stronger absorption capacity than kaolin. The active minerals in green illite clay include dolomite, magnesium, calcium, potassium, manganese, phosphorus, zinc, aluminium, silicon, copper, selenium, and cobalt, as well as a small percentage of montmorillonite. The green colour comes from a combination of iron oxides and decomposed plant matter, primarily kelp and algae (which is also why brighter green clays are considered higher quality than grey-green ones).

In a shampoo bar formula for oily hair, French green clay contributes stronger oil absorption than kaolin alone would provide. Using both gives the formula a graduated effect: kaolin provides the baseline gentle cleansing and slip, while the green clay steps up the oil absorption for a scalp that genuinely needs it.

At 2.6% of the formula, the green clay inclusion is decent without being aggressive. This is a bar designed for regular use, not a weekly clarifying treatment, so the balance matters.

The complete clay comparison across all eight clays tested in Batch and Bubble syndet bars is at every clay I’ve tested in syndet bars, covering absorption, colour, and which suits your formula.

What the other ingredients do

The surfactant base follows the same logic as other oily hair syndet formulas on this site. SCI at 65% provides the primary cleansing action – it is a mild surfactant that produces a dense, creamy lather and rinses cleanly. CAPB at 15% is the secondary surfactant, boosting lather and adding mildness to the formula. Together they clean thoroughly without the stripping effect that gives conventional sulphate shampoos their reputation for producing rebound oiliness which is explained in detail in the transition period biology article.

Cetyl alcohol at 10% provides the structure that holds the bar together and contributes a small amount of conditioning to the hair shaft without adding weight. At this percentage it is doing its structural job first and its conditioning job second, which is the right balance for an oily hair formula.

Jojoba oil at 2.4% is included for its ability to condition the hair shaft and scalp without heaviness. Jojoba is technically a liquid wax rather than an oil, which means it does not behave like heavier oils in a formula and is less likely to contribute to greasiness at the scalp. It is a well-suited inclusion for an oily hair bar at low percentages.

Glycerine at 1% is a humectant that draws a small amount of moisture to the hair shaft. At this level the effect is subtle, but it contributes to the finished texture of the bar and the feel of the hair after washing.

Why rosemary?

Rosemary essential oil has a genuine research history behind it, more so than most cosmetic botanical ingredients. Studies have found rosemary oil to be a comparable treatment to minoxidil for androgenic alopecia, and it may support hair growth through improved scalp circulation and antioxidant activity. A 2024 randomised controlled trial published in NCBI found that rosemary oil significantly improved hair growth rate, thickness, density, and length compared to controls, with hair growth rate increasing by up to 57% from baseline over 90 days.

However, there is an important caveat that applies directly to this recipe. Those studies use rosemary oil as a leave-in or topical application which is massaged into the scalp and left to absorb. This recipe is a rinse-off product. The bar is on your scalp for the duration of a wash and then rinsed away. Whether meaningful levels of rosemary’s active compounds are absorbed through the scalp during a rinse-off application is unknown, and I have not tested this bar over a long enough period to observe any effect on hair density or growth.

I included rosemary for two reasons I can speak to honestly: its scent, and the pleasant warming sensation it produces on the scalp during washing.

That warmth comes from 1,8-cineole (eucalyptol), the dominant compound in the non-camphor rosemary chemotype, which is known to stimulate local circulation. It is the ingredient doing what rosemary is known for, even in a brief rinse-off contact. Whether that brief stimulation translates to measurable hair growth over time is a claim this recipe cannot make. What I can say is that the sensation is pleasant, not harsh, and my scalp felt noticeably invigorated after washing.

If rosemary’s hair growth reputation is your primary interest, a leave-in rosemary oil treatment applied directly to the scalp and left on is a better-evidenced approach than a shampoo bar. This bar uses rosemary because it works well in the formula and the scalp experience is good. The hair growth properties are a reasonable hypothesis, not a tested outcome.

Honest results from testing

The bar cleans as well as the standard oily hair syndet bar, maybe even a little better. Lather is good, rinse is clean, and the scalp feels genuinely clear after washing rather than stripped.

The warmth from the rosemary is noticeable during washing and fades quickly after rinsing. It sits in the range of pleasant rather than intense…I’d say it’s comparable to the mild tingle of a peppermint product but warmer and less sharp. People with sensitive scalps should patch test before committing to a full wash, as any scalp-stimulating ingredient can cause irritation on reactive skin.

The scent during washing is present and recognisably rosemar: herby, slightly woody, not medicinal. It fades significantly by the time hair is dry. If you want a fragrant bar that holds its scent through the day, this is not that bar. If you want something that smells pleasant in the shower and then gets out of the way, it performs well.

Personally, rosemary is not my favourite scent, but I can see why it would suit people who prefer herbal over floral or citrus. It is a clean, purposeful smell that fits the nature of the bar.

Bar texture and hardness after the seven-day cure is good. The clay content gives the finished bar a slightly more matte appearance than a plain surfactant bar, which is visually appealing and a useful indicator of what the clays are doing.

A note on the clays and water

Both kaolin and French green clay are insoluble in water, meaning they do not dissolve but suspend in the lather during washing and are rinsed away along with the surfactants. In hard water areas, clay particles can occasionally leave a very slight residue if rinsing is insufficient. Rinse thoroughly, particularly at the scalp, and this is unlikely to be an issue. If you are in a hard water area and experiencing any residue or dullness, the hard water and shampoo bars guide covers the options.

Where this bar sits in the Batch and Bubble range

This bar is designed for oily to normal-oily hair which are scalps that produce enough sebum to need stronger cleansing than the standard bar provides, but that are not experiencing a clinical scalp condition. If your scalp is reactive, inflamed, or prone to dermatitis, the additional stimulation from both the rosemary and the stronger clay absorption may not be appropriate, and starting with the gentler formula is a better entry point.

If you want to know more about why your hair gets greasy when you switch to shampoo bars, read the article here. And if you are trying to understand why your hair might be greasier than expected after switching to a syndet bar, the transition period biology article explains the mechanism before you decide whether a stronger formula is actually what you need.

If you’re not sure if this bar is for you, take the Batch and Bubble hair type quiz to find out:

Written by Neets at Batch and Bubble
DIY personal bathroom care recipes for real life.
www.batchandbubble.com