Sam McKnight, the hairstylist behind some of fashion's most iconic hair looks, has launched the Cool Girl Body Plumping & Volumising Cream (£29), a hybrid formula designed to tackle flat hair by strengthening strands from within. Unlike traditional volumisers that merely coat the hair, this cream combines styling and care to create fuller-looking volume while improving hair resilience over time.
For those with famously fine, stubbornly flat hair, the quest for volume is often a losing battle. As a reviewer with such hair, I've tried volumising mousses that leave lengths crispy, texture sprays that make hair both dry and greasy, and endless rounds with a hot brush in search of lift that lasts longer than a commute. When Sam McKnight launched Cool Girl Body, I was intrigued—especially given my existing love for his 'Cool Girl' range and its divine scent.
What Makes Cool Girl Body Different?
According to the brand, one of the biggest reasons hair loses volume isn't always the wrong styling products but weakened hair fibres caused by heat styling, colouring, environmental damage, and general wear. When hair becomes compromised, it struggles to hold shape and elasticity, causing freshly blow-dried roots to flatten throughout the day. Cool Girl Body addresses both problems at once.
The cream uses a cocktail of ingredients to plump individual strands, create separation between hairs for fuller-looking volume, and provide flexible hold without stiffness. It also contains conditioning and strengthening ingredients to improve resilience, plus heat and humidity protection—welcome given Britain's tendency to serve four seasons in a single afternoon. As Sam McKnight describes it, the volume looks 'healthy, smooth and soft, never stiff or overloaded.'
The Science Behind the Formula
The technology is notably interesting. Hero ingredients include Voluminis™, which increases the density of individual strands while pushing hairs away from one another, creating the illusion of fuller hair. Biostyle CGP™ is a sculpting polymer that provides lift at the roots and helps hair maintain shape, even in humidity. Yerbaluxe® Crown conditions and strengthens stressed hair fibres, improving elasticity, while SymHair Thermo™ offers heat protection up to 230 degrees and shields against humidity.
The idea is simple: stronger hair holds volume better. Given years of bleaching, heat styling, and aggressive brushing, this logic feels entirely sound.
My Review
As expected, the texture and scent were everything I'd expect from Sam McKnight. It has a silky, thick consistency—the kind I'd usually avoid with fine hair, fearing greasiness or heaviness. But it did anything but. I used about a 10p-sized amount, worked it through my palms and fingers, then ran it through my hair. Once dried, my strands definitely felt thicker, and the volume was subtle rather than dramatic, with potential to build with more practice and the right tools. I'd love to try it with a hot styling brush next to maximise volume.
Most importantly, despite the added thickness, my hair didn't feel heavy or as though it had extra product in it. With more experimenting, I'm sure I could get closer to the 'higher the hair, the closer to God' level of volume Dolly Parton often discusses. While I've learned not to trust every product promising 'big hair', Cool Girl Body feels like a more thoughtful approach—focusing on creating the conditions for fuller-looking hair while supporting hair health, rather than merely masking the issue with heavy styling agents.
For anyone with flat, fine hair, this product offers a promising solution that combines immediate volume with long-term hair strengthening. It's available to purchase now for £29, and given its hybrid nature, it may just be the hair product flat-haired girls need to know about.
