A thermal round brush is the tool that actually produces a blow-out. The dryer supplies heat and air; the brush supplies tension and shape, and tension is where volume, smoothness and a lasting bend all come from. Nine of the thirty Avanti tools at ProHair are thermal round brushes, which tells you how much of the work this category does.
Choosing one comes down to three decisions: barrel diameter, barrel construction, and handle. This guide takes them in that order, because that is the order of importance.
Decision one: barrel diameter, set by hair length
This is the decision people get wrong, and the rule is simpler than the marketing suggests: the brush needs at least one full wrap of hair around the barrel to do anything. Less than one wrap and you are dragging, not shaping. Far more than one wrap and you are spending three passes on what a bigger barrel would do in one.
| Barrel | Hair length | What it does |
|---|---|---|
| 25 mm (1") | Above the jaw — pixies, short crops, fringes | Grips short sections a large barrel simply cannot hold. Also the barrel for shaping around the face on any length. |
| 33 mm (1.25") | Chin to collarbone — bobs and lobs | The all-rounder, and the barrel most salons reach for by default. Enough wrap to shape, small enough to still get lift at the root. |
| 43–44 mm (1.75") | Past the shoulders | One wrap covers what a small brush needs three passes to do. Smoother result, far less arm. |
| 53 mm (2") | Below the shoulder blades | On very long hair there is no substitute. Anything smaller doubles your section count. |
Avanti covers the full ladder twice over. The plain ceramic line runs 25 mm, 33 mm, 43 mm and 53 mm. The gel-handle line runs 25 mm, 33 mm, 44 mm and 53 mm.
If you own one brush, make it 33 mm. It is the barrel that handles the widest range of heads, and the one a stylist would keep if forced to choose. If you own two, add the size that matches your own length — a 33 for the crown and a 44 or 53 for the lengths is the combination that makes long hair manageable.
Decision two: what the barrel is made of
Ceramic
A ceramic barrel absorbs heat from the dryer and holds it, so the brush is working the hair from the inside of the wrap while the dryer works the outside. That is the whole mechanism behind a smooth, long-lasting blow-out, and it is why a thermal brush outperforms a plastic round brush of the same size by a wide margin. Every Avanti thermal round brush has a ceramic barrel.
Vented versus solid
The plain ceramic brushes have vented barrels — holes through the barrel let hot air pass through the wrapped section rather than only around it. Vented is faster, and it is the better choice if your hair is thick or if you are drying a lot of it. A solid barrel holds more heat and presses the cuticle harder, which reads as more shine on fine or medium hair and is the better choice if smoothness matters more to you than speed.
Bristles
Most of the range uses nylon bristles: firm, durable, and enough grip to pull a section taut. The exception is the Avanti Ultra Extra-Long Ceramic Thermal Round Brush, which uses a mixed boar-and-nylon fill on a ceramic, aluminium and wood body. Boar bristle is finer and closer-packed, so it catches more of the cuticle and distributes the hair's own oils down the strand — noticeably more polish, at the cost of grip on very thick hair, where the nylon in the mix does the holding. It is also the longest barrel in the range, which is why it is the brush for hair below the shoulder blades that hangs off the end of a normal brush.
Decision three: the handle
This is not a cosmetic choice, and it is the one thing that separates two otherwise identical brushes in the Avanti line-up.
The gel-handle brushes carry a silicone grip. If you are a stylist doing back-to-back blow-dries, or anyone whose hand cramps or whose wrist aches through a long brush-out, the cushioned grip is the only thing on the spec sheet that will change your day. It takes measurably less force to hold, and less force means less compensating with your shoulder.
The plain ceramic brushes are the same barrel with a hard handle, at a lower price. If you are drying your own hair two or three times a week, that is a perfectly reasonable place to save.
Using a thermal brush properly
- Get to 80% dry first. A round brush on wet hair stretches the strand and breaks it. Rough-dry with fingers or a skeleton brush, then start.
- Clip the rest of the head away. Work in sections no wider than the brush is long.
- Tension is the whole technique. Pull the section taut from root to end. A slack section will not smooth no matter how hot the air is.
- Nozzle pointing down the strand, following the brush, never against it.
- For root lift, over-direct: lift the section straight up, or slightly past vertical, and dry it there.
- Let the barrel cool in the hair for a few seconds at the end of each section, then slide out. Hair sets as it cools — this is the step that makes the shape last.
Cleaning, and when to replace
Pull shed hair out of the bristle bed after every few uses — with a vented barrel, hair trapped inside the vents blocks the airflow you paid for. Once a month, wash the bristle bed with warm water and a drop of shampoo, shake it out and dry it bristles-down. Never soak a wooden-bodied brush. Replace when bristles start splaying or when the tips wear off nylon bristles, because a worn tip scratches the scalp.
Straight answers
- Short hair, one brush → 25 mm
- Bob or lob, one brush → 33 mm
- Long hair, one brush → 43 mm or 53 mm
- Very long, wants maximum polish → Extra-Long, mixed boar and nylon
- Working stylist, or sore hands → any of the gel-handle versions
Keep reading
The Complete Avanti Buying Guide · Hair dryers · Cushion, vent and skeleton brushes