When extension lengths feel rough or keep catching on a brush, “more moisture” sounds like the obvious answer. But softness involves more than water. How easily individual hairs slide past one another matters too.
A treatment mask brings together ingredients with different jobs: conditioning agents that interact with the hair’s surface, oils and butters that contribute to its feel, and ingredients that hold the cream together. Understanding those jobs makes an ingredient list much more useful.
Here, we look inside Hadrill’s The Treatment Mask and explain what hair-fibre research can tell us about conditioning natural hair and human-hair extensions. The studies discussed examine ingredients or experimental formulas; they are not tests of the finished Hadrill mask.
Why conditioning matters for human-hair extensions
Human-hair extensions are made from the same kind of keratin fibre as the hair growing from your scalp. Once collected, they are no longer attached to the follicle and its oil-producing structures. Their processing history also matters: bleaching, colouring and repeated styling can change the surface you are caring for.
The outer layer of a hair, the cuticle, consists of overlapping cells. Damage to that surface and its natural lipid layer can increase friction, making the hair feel less smooth. Hair fibres cannot biologically heal themselves; conditioning works by changing their surface behaviour and feel. Research on conditioner performance therefore measures practical outcomes such as the force needed to comb treated hair. Research on hair lubrication and conditioning.
For extension wearers, this makes slip and manageability particularly useful goals. The connection to extensions is an application of hair-fibre science, rather than proof that every extension type will respond identically. For recurring knots, our dry and tangled extensions guide explains when your fitting salon should take a look.
The conditioning ingredients that help with slip
One of the first ingredients in The Treatment Mask is behentrimonium methosulfate, often shortened to BTMS. It is a positively charged conditioning surfactant. Its interaction with the hair surface helps explain why a conditioner can make wet hair easier to comb.
A study in the International Journal of Cosmetic Science compared four conditioning surfactants, including BTMS, in experimental formulas. The researchers examined how they deposited on human hair and measured wet-combing work. All four treatments improved combability under the test conditions, although their performance differed. BTMS performed behind behentrimonium chloride and ahead of the two other surfactants tested.
The researchers also measured a chemical marker of oxidative damage. Better combing did not mean that this damage had been reversed. That is a useful distinction: a treatment can improve manageability without restoring hair to its original, unprocessed state. Tham and colleagues, published online 2025.
The Hadrill ingredient list also includes stearalkonium chloride and polyquaternium-11 within its conditioning system. Looking at the whole formula is more informative than choosing a mask solely by its headline oil.
Why a hair mask contains fatty alcohols
Cetyl alcohol and cetearyl alcohol are waxy fatty alcohols. They are different from ethanol, the ingredient usually meant by “alcohol” in everyday conversation. In creams, fatty alcohols help build texture and keep the oil and water components mixed. Fatty-alcohol ingredient information.
That structure affects how a conditioner behaves during use. In a laboratory comparison of experimental conditioners, changing the mixing conditions altered texture, friction and wet-combing performance. The same ingredient names do not automatically produce the same finished result. Ajayi, Davies and Amin, 2021.
Our mask also lists Alcohol separately. It would therefore be inaccurate to describe it as alcohol-free, or to assume that every alcohol on the label is a fatty alcohol.
What the eight plant oils contribute
The Treatment Mask contains sunflower, olive, sweet almond, macadamia, babassu, castor, jojoba and argan oils. They form its plant-oil blend, alongside shea butter. You can see their individual INCI names in the full ingredient list.
Oil research helps explain why the type of oil, the amount applied and the time it stays on the hair all matter. It does not support treating eight oils as eight interchangeable repair treatments.
Argan oil: research on protection before damage
In a 2022 study, researchers applied argan oil to cut human-hair tresses before exposing them to an oxidising treatment. The pretreated hair showed significantly less protein loss than the comparison group. Instrumental analysis also detected oil remaining after washing.
This is relevant evidence that argan oil can interact beneficially with hair under specific conditions. However, applying oil before an oxidising treatment differs from using a finished mask after shampooing. The study does not establish that our mask prevents bleaching damage or repairs existing damage. Sharifi and colleagues, 2022.
Sunflower and olive oils: the surface matters too
A study of oils on human hair examined changes in the forces between fibres and in reflected light. The researchers interpreted changes over time as evidence of oil-film thinning and absorption into the hair. Olive and sunflower oils were among those examined; the methods and results varied between oils.
These experiments involved directly applied oils, including observations after 24 hours. They do not tell us that every oil in a rinse-off mask reaches the centre of an extension in five minutes. Surface effects are part of the science too. Keis and colleagues, 2005.
For sweet almond, macadamia, babassu, castor and jojoba, this article does not assign a separate, clinically proven extension benefit to each oil. They are components of the blend; its combined performance depends on the finished formulation. Babassu is also a different ingredient from coconut oil, so coconut-oil findings should not be presented as tests of babassu.
Hydration, softness and oil are different things
An oil does not add water to hair. It can change how water moves into and out of the fibre.
Researchers investigating coconut, mineral and sunflower oil films found that oil-treated hair generally took up less water vapour than untreated hair. The films also slowed moisture diffusion, which can slow moisture loss. This helps explain why the word “moisturising” needs care: a treatment’s effect is not simply about making hair absorb as much water as possible. Keis, Huemmer and Kamath, 2007.
The mask also contains glycerin, a humectant: an ingredient with water-binding properties. Cosmetic Ingredient Review lists both humectant and hair-conditioning functions for glycerin. Its presence explains a different formulation role from that of an oil, without telling us exactly how much moisture remains in hair after rinsing. Glycerin ingredient assessment.
Aloe vera leaf juice is another component, and shea butter contributes to the formula’s fat-based ingredients. Shea butter is also used to influence cosmetic texture. These ingredients belong in the explanation of the complete cream; their presence alone is not a measurement of deep hydration inside extension hair. Shea ingredient assessment.
Where biotin, propolis and the other ingredients fit
The label includes biotin, propolis, vitamin E in the form of tocopheryl acetate, and several botanical extracts. These should not be confused with proof that a rinse-off mask makes extensions grow or regenerates their fibres.
For example, a 2025 biotin study used a specially formulated leave-on scalp serum, applied daily for three months. It involved 22 participants and had no placebo group. That is a different treatment and outcome from conditioning extension lengths. Likewise, published propolis hair-growth research has examined living follicles in mice. Neither is evidence of repair to detached extension hair. Biotin serum study; propolis study.
Other ingredients help make the product usable as a cream. Emulsifiers support the mixture of oil and water; the preservation system helps protect the product during use; fragrance contributes its scent. Each ingredient need not perform a separate hair-repair function to have a purpose in a formula.
Using The Treatment Mask on extensions
The Treatment Mask is Hadrill’s protein-free treatment step for natural hair and extensions. Follow your extension supplier’s aftercare guidance alongside the product directions:
- Wash with The Shampoo, then rinse.
- Smooth the mask through damp mid-lengths and ends, keeping it away from tapes, bonds and other attachment points.
- Leave for five to ten minutes, then rinse thoroughly.
- Follow with The Conditioner.
Use the mask one to two times weekly, as directed. Our shampoo, mask and conditioner guide explains how the steps fit together; all three products are available in The Trio.
Consistent conditioning and gentle handling are useful parts of caring for the hair you have invested in. Claims that a particular mask extends the life of extensions by a set number of weeks or months would need testing on that finished product and those extensions. The practical aim of this routine is softer-feeling, more manageable lengths, cared for without pulling at their attachments.