Modern shampoos are designed to do more than cleanse — they also condition, nourish, and protect the hair1. To achieve these multifunctional benefits, formulators commonly incorporate oils, particularly silicone-based ones, into shampoo systems. However, adding oils to a water-based formulation is far from straightforward. Oils must first be pre-emulsified before incorporation to ensure product stability and consistent performance in terms of lathering, viscosity and conditioning.
Shampoos are primarily aqueous surfactant systems that remove dirt and sebum through micelle formation. Because oils are hydrophobic, they do not dissolve or disperse naturally in water. When added directly, oils tend to separate and float on the surface, leading to phase separation and visible oil layers. Moreover, un-emulsified oils can disrupt micelle organization, diminishing both cleansing efficiency and foam formation. Foam generation in shampoos relies on surfactants occupying the air–water interface; oils compete with these surfactants, thereby reducing foam volume and stability. In addition, the presence of oil can significantly alter the viscosity of the system — sometimes increasing it at low concentrations, but often thinning it or destabilizing the formula when not properly dispersed.
Pre-emulsification transforms these otherwise incompatible components into a stable, functional dispersion, enabling formulators to maintain both technical performance and sensorial quality. In essence, pre-emulsifying oils is not merely a formulation preference — it is a scientific necessity for creating high-quality, well-balanced shampoos.
To date, most water-insoluble silicone oils used in shampoos are pre-emulsified prior to formulation. However, pre-emulsified non-silicone oils have not been widely reported in the literature. This study investigates the application of a shea butter submicroemulsion as the first non-silicone oil emulsion designed for transparent, silicone-free, sulfate-free conditioning shampoos.
Why Shea Butter?
Shea butter, a lipid-rich extract derived from the kernels of Vitellaria paradoxa (Sapotaceae), has gained widespread use in cosmetic and dermatological formulations due to its high content of fatty acids, unsaponifiable lipids2-4. Its unique fatty acid profile — primarily contains stearic acid (C18:0) around 31.2 to 45.1% and oleic acids (C18:2) around 43.3-56.5%, offers occlusive and moisturizing properties, making it a desirable ingredient in cosmetics and dermatological applications2-5.
In addition, shea butter also contains unsaponifiable ingredients: tocoperols (α, β, γ,δ); phenols such as gallic acid, catechin, epicatchin, gallate, galloctechin, quercetin and trans-cinnamic acid; sterols such as α-spinasterol and △7-stigmasterol, campesterol and β-sitosterol; triterpenes such as acetyl triterpenes and cinnamyl triterpenes and triterpene alcohols such as αamysine, β amyrine, butyrospermol and lupeol. These ingredients in shea butter help provide anti-oxidation property2,6-7, UV-Vis absorption property3,6, antimicrobial activity7-8 and anti-inflammatory property9-11.
Shea butter has been widely researched in usage for pharmaceutical ointments, creams, emulsions and nanoparticle formulations for its natural origin, easy penetration to skin and synergy for active ingredients release and penetration8,11-13. However, incorporating shea butter into stable emulsions presents significant formulation challenges.
Firstly, to make a stable emulsion, hydrophile-lipophile balance (HLB) value of the surfactant or surfactant combination needs to be very close to the required HLB (RHLB) value of the oil phase14. To find a proper HLB emulsifier combination close to RHLB is time consuming. J. A. Isaac et al. found 5:5 span 20/ tween 20 (HLB 12.7) was relatively stable for emulsifying their honey-shea butter emulsion after a series formulation experiments. The emulsion particle sizes were 6.997 μm initially, 6.844 μm at 4℃, 7.022 μm at 25℃, 8.546 μm at 40℃ after 3 months15, which were quite big although they were satisfied by the stability.
Normally the average particle size of a macroemulsion is about 1- 2 μm, at a range from 0.1 – 5 μm16. A. O. Oyedele used shea butter/ liquid paraffin blends and potassium hydroxide (KOH, to neutralize the fatty acid in shea butter and worked as an emulsifier) to make a stable fluid emulsion through series ratio of shea butter/ liquid paraffine and different KOH concentrations, and he found the most stable formulation contained 4.5% w/w shea butter emulsified with 0.2M KOH, the mean emulsion particle size was 4.4μm17.
Secondly, owing to its semi-solid crystalline nature at room temperature and its unique fatty acid profile (high quantity of stearic acid), shea butter tends to form crystalline in the lamellar phase of the emulsion. This swollen crystalline lamellar phase is not only sensitive to temperature but also to processing variables. During cooling or storage, it can destabilize the interfacial film of emulsions, leading to coalescence or viscosity drift, which will affect the stability of the emulsion18.
Thirdly, the creamy and thick texture due to the high content of stearic acid in shea butter contributes to poor spreadability and a tacky feel, which may negatively impact consumer sensorial perception19. O. Ayanlowo et al. made a survey in Nigerians who use shea butter. Among 228 medical practitioners, 32.1% reported shea butter was too thick, 25.5% reported shea butter was sticky19.
Given these limitations, improving the emulsification efficiency and sensory profile of shea butter-containing systems remains a significant challenge for cosmetic formulators. There is growing interest in developing non-ionic, submicron emulsions that can enhance stability, spreadability and skin aesthetics, while retaining the moisturization and nourishing benefits of shea butter.
HARMONIE Shea Butter Emulsion (hereinafter referred to as HSBE) is a pre-formulated, non-ionic submicroemulsion where shea butter is stably emulsified into submicron-sized particles (<1 µm) using a tailored blend of surfactants. HSBE is designed to overcome the core limitations of raw shea butter, namely, instability, poor spreadability and tacky sensory attributes, while retaining its moisturizing and nourishing benefits.
Non-silicone shampoo is well accepted by consumers nowadays due to the clean beauty trend and sustainability requirements. However, the squeakiness during rinsing remains an unsolved problem compared to silicone shampoo. In this study, we evaluated HSBE in silicone-free amino acid type of shampoo formulations and benchmarked it against pure shea butter (Shea Butter RF). The results revealed that HSBE not only improved combing and hair conditioning properties, but also significantly enhanced sebum and scalp cleansing performance, compared to both the blank formula and pure shea butter. Furthermore, HSBE formulations exhibited an interesting transition from initial turbidity to final transparency, suggesting improved solubilization behavior in amino acid–based surfactant systems and good stability.
Preparation of Transparent Silicone-Free, Sulfate-Free Shampoo
Two types of Shea Butter oils were used for this study:
- HARMONIE Shea Butter Emulsion (HSBE): INCI Name: Water, Butyrospermum Parkii (Shea) Butter, C12-13 Pareth-3, C9-12 Alkane, Glycerin, C12-13 Pareth-23, Poloxamer 188; Manufactured by Momentive Performance Materials Inc.
- Shea Butter RF (hereinafter referred to as Raw SB): INCI Name: Butyrospermum Parkii (Shea) Butter; Manufactured by Kokyu Alcohol Kogyo Co., Ltd.
The shampoo formulations were prepared according to the composition presented in Table 1.
| Phase | INCI Name | Blank (wt%) | Shampoo with HSBE (wt%) | Shampoo with Raw SB (wt%) |
|---|---|---|---|---|
| A | Water | To 100 | To 100 | To 100 |
| Polyquaternium-10 | 0.5 | 0.5 | 0.5 | |
| B | Lauryl Hydroxysultaine | 16.67 | 16.67 | 16.67 |
| C | Sodium Methyl Cocoyl Taurate | 33.33 | 33.33 | 33.33 |
| Disodium EDTA | 0.05 | 0.05 | 0.05 | |
| Sodium Benzoate | 0.25 | 0.25 | 0.25 | |
| Citric Acid | 0.27 | 0.27 | 0.27 | |
| D | Water, Butyrospermum Parkii (Shea) Butter, C12-13 Pareth-3, C9-12 Alkane, Glycerin, C12-13 Pareth-23, Poloxamer 188 | - | 1.0 | - |
| Butyrospermum Parkii (Shea) Butter | - | - | 0.28 | |
| Cocamide Methyl MEA | 2.5 | 2.5 | 2.5 | |
| Butylene Glycol Laurate | 0.5 | 0.5 | 0.5 | |
| E | Phenoxyethanol | 0.4 | 0.4 | 0.4 |
| Fragrance | 0.5 | 0.5 | 0.5 |
During preparation, Phase A ingredients were first combined and heated with gentle stirring until a homogeneous mixture was obtained. Phase B was then added to Phase A, and the blend was heated to 80 °C to ensure complete dispersion. Next, Phase C ingredients were incorporated and mixed until fully dissolved. The mixture was subsequently cooled to below 60 °C, followed by the addition of Phase D, which was blended until uniform. Finally, the formulation was cooled to below 45 °C, and Phase E was introduced to complete the shampoo preparation.
As shown in Table 2, the addition of HARMONIE Shea Butter Emulsion (HSBE) to the shampoo formulation resulted in a decrease in both viscosity and transmittance 24 hours after preparation. Viscosity was measured using a Brookfield DVⅡ+ viscometer at 25 °C, employing a No. 06 spindle at 20 rpm for 30 seconds. The results indicate that increasing the HSBE concentration leads to progressively lower viscosity values. Despite this viscosity reduction, all samples remained transparent and physically stable several days after preparation, confirming that the incorporation of HSBE did not induce phase separation or cloudiness.
| Property | Blank | Shampoo with HSBE 1.0% | Shampoo with HSBE 1.5% | Shampoo with HSBE 2.0% |
|---|---|---|---|---|
| pH | 5.48 | 5.49 | 5.49 | 5.48 |
| Viscosity (mPa.s) | 1850 | 1100 | 900 | 800 |
| Shampoo Appearance | Transparent | Transparent after a few days | Transparent after a few days | Transparent after a few days |
Lather performance was evaluated using the blender foam volume drainage method. Each shampoo sample was diluted to a 10% (w/w) aqueous solution with warm water (~40 °C). To simulate sebum contamination, 0.14 g of liquid lanolin was added to 7 g of the diluted shampoo, and the mixture was combined with 150 ppm hard water at approximately 40 °C. The sample was agitated for 10 seconds, then transferred into a graduated cylinder. The initial foam height represented foam generation, while the liquid–foam interface height recorded after 3 minutes and 30 seconds reflected foam stability.
Figure 1 - Lather performance test of shampooCourtesy of Beauty Hi-Tech Innovation, Momentive Performance Materials
As illustrated in Figure 1, the incorporation of 1.0% and 1.5% HSBE showed no significant influence on foam volume or stability compared with the control. However, at 2.0%, both foam height and stability were noticeably reduced, suggesting that excessive emulsion content can interfere with surfactant foaming efficiency.
Figure 2 - Sebum cleansing index of shampoo samples Courtesy of Beauty Hi-Tech Innovation, Momentive Performance Materials
Combing performance was evaluated at both the “after rinse” and “dried” stages. As shown in Figure 2, formulations containing 1.0% and 1.5% HSBE demonstrated improved combing ease in both wet and dry conditions. In contrast, the 2.0% sample exhibited a negative effect on combing performance after drying, likely due to excess deposition that increased friction on the hair surface.
Based on these findings, an HSBE concentration of 1.0% appears to provide the optimal balance between conditioning efficacy, foaming stability and overall formulation performance for transparent, silicone-free, sulfate-free shampoos.
Cleansing Effect
Shampoos containing 1.0% HSBE and 0.28% raw shea butter (Raw SB) were compared to evaluate their cleansing performance. Approximately 1.0 g of artificial sebum20 was applied evenly to bundles of dried, healthy Asian hair. Each treated hair bundle was then mounted on an SK-7A dynamic combing tester, followed by the application of 1.0 g of shampoo.
The hair bundle was processed on the dynamic combing tester according to the following sequence:
1. Comb the bundle five times with the shampoo applied
2. Comb five times under a warm-water shower (~40 °C)
3. Comb three times without rinsing.
After treatment, the samples were air-dried overnight, then further dried in an 80 °C incubator. The sebum cleansing rate was calculated using the following equation (N = 3):
Sebum Cleansing Rate (%) = (Weight of sebum rinsed off / Weight of sebum applied) ×100
Composition of artificial sebum20: soybean oil (48%), oleic acid (13%), myristic acid (12%), squalene (12%), paraffin (10%), glyceryl oleate (3%), and cholesteryl stearate (2%).
The results showed that the shampoo containing HSBE achieved a ~6% higher sebum cleansing rate compared with the control formulation without added oil. Furthermore, as illustrated in Figure 2, the HSBE-containing shampoo demonstrated a significantly higher cleansing efficiency than the formulation containing raw shea butter, indicating that the pre-emulsified form of shea butter enhances oil dispersion and cleansing capability within the shampoo matrix.
Based on the above observations, the enhanced cleansing performance of the HSBE-containing shampoo can be explained by the principle of similarity and solubility. Shea butter, being a lipid-based material, can partially dissolve or solubilize scalp sebum due to their similar chemical nature. In the case of HSBE, which is a submicroemulsion of shea butter, the significantly smaller droplet size allows for more effective interaction with and encapsulation of sebum components on the scalp surface. This fine dispersion promotes efficient emulsification and removal of oily residues during rinsing, thereby improving overall cleansing performance.
In contrast, raw shea butter, with its higher surface tension and larger particle size, is less able to spread and deposit uniformly on the scalp. It does not readily mix with sebum during washing, and may instead consume part of the surfactant activity that would otherwise contribute to sebum emulsification and removal. As a result, shampoos containing pure shea butter show lower cleansing efficiency compared with those incorporating pre-emulsified shea butter submicroemulsions.
Combing Performance
Applying 1.5g of the test sample to a bundle of healthy Asian hair, we used the dynamic combing instrument SK-7A to treat the hair bundle with the following procedure21-22:
- Comb the hair bundle 5 times
- Comb the hair bundle 10 times under a warm water shower
- Turn off the shower and comb the hair bundle 5 times
- Naturally dried overnight
- Comb the hair bundle 4 times
The resulting combing force data was divided into five stages: lathering first half of the rinsing stage, second half of the rinsing stage, after-rinse and dried. N=3. Lower values indicate better combability.
Figure 3 - Dynamic combing performance testCourtesy of Beauty Hi-Tech Innovation, Momentive Performance Materials
Compared with the blank shampoo (without HSBE), formulations containing 1.0% and 1.5% HSBE exhibited a significant reduction in combing force at both the after-rinse and dry stages. This improvement indicates an effective conditioning benefit, attributed to the deposition of shea butter components from the HSBE emulsion onto the hair surface.
Overall, the experimental results demonstrate that incorporating 1.0–1.5% HSBE into a sulfate-free shampoo can enhance hair combability and conditioning performance without notably affecting lather volume or stability. In contrast, increasing the HSBE concentration to 2.0% led to a noticeable reduction in viscosity and deterioration in foam characteristics, while providing no additional improvement in conditioning efficacy. Therefore, an HSBE concentration of around 1.0% appears to be the optimal level for balancing cleansing, foaming, and conditioning performance in transparent, silicone-free, sulfate-free shampoo formulations.
Scalp Hydration Effect
In addition to its hair conditioning benefits, the effect of the HSBE on scalp care, scalp moisturization in particular, was also investigated following the procedure below. Four panelists applied a 1% HSBE shampoo to their left part and a blank shampoo to the right part. No hair conditioner was used.
- Washed, wiped and dried hair (by hair dryer)
- Waited for one hour under room temperature. Initial scalp water content was measured using DermaLab Combo 4, Hydration Pin Probe (manufacturer: Cortex Technology), then scalp water content after shampoo were measured.
- Three sets of spots on the scalp were selected symmetrically on right and left sides; each spot were measured three times and an average data were obtained.
Figure 4 - Scalp hydration enhancement testCourtesy of Beauty Hi-Tech Innovation, Momentive Performance Materials
As shown in Fig. 4, the shampoo containing HSBE increased scalp hydration by 21 ± 6%, compared with −1 ± 5% for the blank shampoo, indicating that HSBE provides a significant scalp-moisturizing effect. This observation aligns with the well-established recognition of shea butter for its strong skin-moisturizing properties, making it highly relevant in the current era of scalp-care focus.
Conclusion
Transparent, silicone-free conditioning shampoos are distinctive because they embody a technological balance between clarity and care. Through microemulsion technology and precise ingredient design, these formulations deliver a visibly pure yet sensorially rich experience — cleansing effectively like a conventional shampoo while conditioning lightly, reflecting the sophistication of modern hair care formulation science.
Shea butter and other vegetable oils typically exhibit low solubility in amino acid–based surfactant systems, which often limits their application in transparent shampoo formulations. However, when shea butter is pre-emulsified into a stable submicroemulsion, as in HARMONIE Shea Butter Emulsion (HSBE), it can be successfully incorporated into transparent, silicone-free, sulfate-free shampoos without causing instability or phase separation.
Experimental results demonstrate that the inclusion of 1.0–1.5% HSBE in a sulfate-free shampoo enhances combing performance while maintaining satisfactory lather quality and transparency. These findings confirm that pre-emulsified shea butter provides an effective, natural alternative to silicone conditioning agents, enabling the development of clear, gentle, and high-performing hair and scalp care formulations.
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