The reason one tool can do two opposite jobs is why a round brush and a dryer can: heat only sets the shape the hair is held in while it cools. A hot air brush grips a section with its bristles and warms it, so the finish is whatever geometry you impose during that heated moment. Pull the section taut and straight and you set it close to straight with a smooth cuticle. Wrap and rotate it around the barrel and lift at the root and you set volume and a soft bend instead. Volume versus straightening is therefore not a property of the brush — it is a property of your hands, decided by three specific choices.
The three choices that decide the finish
The first is tension and direction. Drag the brush down a stretched, taut section and point the airflow and heat downward along the shaft, and the hair cools almost straight with a flattened cuticle — the sleek look. Loosen the tension, curl the section around the barrel and angle the roots upward, and the hair cools with a bend and lift — the volumised look. The barrel does not care which; it faithfully sets whatever shape it is holding when the hair cools.
The second is what you do at the root, because volume is won or lost there and nowhere else. Straightening pulls the roots down and smooth; volumising lifts the brush at the base of the section, holds that lifted root in the heat for a beat, and lets it cool propped up rather than flattened. A hot brush can make hair look full or can leave it sleek and close to the head depending entirely on whether you lift and cool the root or pull it flat.
The third is the cooling step, which is where the shape you chose actually locks. This is the same rule that governs every heated style — the bonds re-form as the hair cools, not while it is hot — so a curl or bend you never let cool in shape simply relaxes back toward flat. If you want volume to survive the day, hold the lifted, wrapped section until it is cool before releasing; if you want sleekness, draw the section smooth and straight and let it cool that way.
Getting the sleek, straightened blowout
To lean the tool toward straightening, keep the section stretched and taut and pull the brush slowly and steadily down the full length, following it closely so the bristles lay the cuticle flat as they pass. Angle the barrel and any airflow downward along the shaft rather than up at the root, and finish each section the way you started it — smooth and down. Slow is the secret here; a fast pass sets no shape, whereas a slow, tense one gives the hair time to heat through and cool close to straight.
Because a hot brush sets a rounded, tensioned section rather than pressing hair flat between two plates, its 'straight' is a softened, glossy, frizz-free straight with a little body — closer to a sleek blowdry than to a flat-ironed finish. If that smooth-but-not-board-straight look is what you want, this is the easiest single tool to get it with. If you specifically need glass-straight, however, the hot brush will plateau below a straightener's flatness, and that is a reason to reach for an iron rather than to change your technique.
The finishing detail that separates a good sleek blowout from a great one is directing the last pass downward and cool. Smoothing the cuticle in one direction and letting it cool flat is what delivers shine and controls frizz, and it is exactly why the two looks diverge so reliably from the same barrel — the sleek version spends its cooling step pressed down, while the volume version spends it held up.
Getting the volumised, bouncy blowout
To lean the same tool toward volume, work the way the round brush does rather than the way the straightener does. Take a section, wrap it around the barrel so the bristles hold it under gentle tension with a curve, and lift at the root — hold the brush at the base of the section pointing slightly upward while it heats, so the roots cool propped rather than flattened. Draw the brush through but let the ends curl inward around the barrel, and you get body through the mid-lengths and a soft bend at the ends.
Barrel size nudges the outcome more than people expect. A larger round brush gives broader, looser volume and a gentle bend, which reads as fullness on long hair; a smaller barrel tightens the curve and adds more defined bounce, but it can look frizzy on short lengths if you overdo it. This is the same diameter logic a curling barrel follows, only applied to the softer shapes a brush can make — if you want to understand why size changes the result, our explainer on choosing a curling barrel size covers the geometry in full.
The realistic ceiling is worth naming so you buy the right expectations. A hot brush adds volume and a bend, but it cannot make a defined curl, and on very fine hair the volume it creates can fade fast unless you nail the cool-before-release step. Two companion reads go further: the explainer on what a hot air brush actually does frames where the whole format sits, and why curls drop early explains the cooling and moisture habits that keep a bouncy blowout from falling flat by lunch.
Key takeaways
- A hot air brush both straightens and volumises; which you get is set by technique, not by the model
- Direction and tension decide it: pull taut and downward for sleek, wrap and lift for volume and a bend
- Volume is won at the root — lift and cool the base propped up, or pull it flat for a sleek finish
- The cooling step locks whichever shape you held, so never release a section before it has cooled
- A hot brush's 'straight' is a soft glossy blowdry-straight, not a flat-ironed finish — it has a ceiling
- Barrel size still matters: a larger round brush gives broad loose volume, a smaller one more defined bounce
Frequently asked questions
Can a hot air brush actually straighten my hair?
It can straighten in the blowout sense, but not the flat-iron sense. A hot brush heats and tensions a section and, pulled slowly and taut with the cuticle smoothed downward, sets hair sleek, glossy and frizz-free with only a very gentle bend — a blown-straight look. What it cannot do is press hair pin-straight between two flat plates the way a straightener can, because a round barrel always leaves a little curve and body. So if your goal is smooth, straight-looking hair with movement, a hot brush delivers it easily; if your goal is glass-straight flatness, you still need a flat iron.
How do I get more volume from a hot air brush?
Focus on the root and the cooling, because that is where volume is actually created. Wrap each section around the barrel, lift the brush at the base of the section and hold it slightly upward while it heats so the roots cool propped rather than flattened, then let the ends curl inward as you draw through. Critically, do not release the section while it is hot — hold the lifted shape until it has cooled, since hair sets as it cools. A slightly larger round brush adds broader volume on long hair, and working on dry, lightly textured hair rather than squeaky-clean slippery hair gives the lift something to hold onto.
Does a bigger or smaller round brush give more volume?
It depends what kind of volume you mean. A larger barrel creates a wider, looser curve, which reads as overall fullness and body through long hair and looks natural and undone. A smaller barrel tightens the bend and gives more defined bounce and lift at specific sections, but on shorter lengths it can edge toward a visibly curled or frizzy look rather than pure volume. For all-over blowout fullness most people prefer the larger round brush; for targeted root lift and bouncier ends a smaller one works better. The principle mirrors curling barrel diameter: bigger shape, softer result.
Will my hot brush give me curls or just waves?
Expect waves and volume rather than true curls, and that is by design. A hot brush tensions hair around a barrel and sets a soft bend, so its range runs from straight-with-body through to a loose, bouncy wave — the classic blown-out finish. It cannot clamp a section onto a fixed mould the way a curling tong does, so it will not produce a tight, defined, springy spiral no matter how you rotate it. If you specifically want curls, a curling iron or wand is the right tool; if you want smooth, full, softly-turned hair, the hot brush is exactly the format built to deliver it.
Keep reading
Buying guide Top 5 Best Hot Air Brushes in Australia: One-Step, Blowout and Multi-Styler Picks Compared
Buying guide Top 5 Best Curling Irons for Long-Lasting Curls in Australia: Automatic, Wand and Multi-Barrel Picks Compared
Product review Dyson Airwrap Multi-Styler and Dryer Complete Long Review (Australia, 2026)
Product review Remington 3-in-1 Curl and Wave Multistyler Review (Australia, 2026)