How to choose a round brush diameter and blow-dry with it

The barrel diameter decides what a round brush does to your hair more than anything else about it. A small barrel makes a tight bend and lifts at the root. A large barrel smooths and gives loose, soft volume. This guide uses the Termix Evolution range, which runs from 17 to 60mm, but the rule works for any thermal round brush.

The rule: a section should wrap about once

Choose a barrel that the hair wraps around roughly once. If it only covers part of the barrel, the brush is too big to shape it. If it wraps around three or four times, you will get a tighter curl than you probably want, and the section takes longer to dry.

Diameter by hair length

• 17mm: fringes, very short cuts, root lift at the crown, and tight curls at the ends.
• 23mm: short layers and pixie cuts, and defined waves on longer hair.
• 32mm: the all-rounder for chin to shoulder length. It smooths a bob and bends the ends.
• 43mm: shoulder length and longer, for smooth lengths with movement.
• 60mm: long hair, for the fastest smoothing and big, loose volume.

If you only buy one, choose by length: 32mm for short to mid-length hair, 43mm for long hair. Then pick the Evolution version that matches your hair's thickness: Soft, Basic, Plus or XL.

Blow-drying with a thermal round brush

1. Towel-dry, apply a heat protectant, and rough-dry to about 80%.
2. Clip the hair into sections, each no wider than the barrel is long.
3. Put the brush under a section at the root and roll the hair around it.
4. Aim the nozzle down the section and follow the brush from root to ends. The vented barrel heats up and helps set the shape.
5. Give each section a blast of cool air before you release it, so the shape holds.

For more volume

At the crown, lift the section straight up from the scalp and dry the root over the top of the brush. A smaller barrel gives the most lift.

FAQ

Why does my blow-dry fall flat?

Usually the barrel is too big for the length, or the section was released while still warm. Go one size down at the root, and cool each section first.

Can I get waves with a round brush?

Yes. Choose a 23 or 32mm barrel, wrap the ends around it, heat them, and cool them before you let go. A heated vented barrel works much like a curling iron here.

Shop every size on the Termix collection page.