Brushing is the cheapest performance gain in climbing. A clean hold has more friction than a dirty one. That's the whole story, really, but it's worth understanding why.
Chalk builds up in the texture of a hold. So does the rubber off your shoes, plus skin, sweat, and dirt. All that gunk fills the tiny pores and crystals that give a hold its grip. Brush it out and the surface bites again. Skip it and you're climbing on a polished, greasy version of the same move. That's true indoors and out, but it matters most on real rock, where bad habits stick around a lot longer.
Why brushing matters
Friction
The texture you're gripping is microscopic. Granite crystals, sandstone grains, limestone pockets: all of it works because the rock is rough at a tiny scale. Chalk and rubber smooth that roughness out. A well-brushed hold can feel like a different grade than the same hold caked in chalk. That's why you see strong climbers brushing between every burn on a hard boulder. They're not stalling. They're resetting the friction.
Etiquette
Brushing is also how you leave a problem the way you found it. Every time you climb, you leave chalk on the holds and chalk marks (tick marks) on the wall pointing at them. Indoors that's mostly a friction problem. Outdoors it's a visual and ethical one too. A boulder covered in white smears and arrows is an eyesore for everyone who shows up after you, and on some rock it speeds up wear. The rule's simple: clean up after yourself.
How to brush a hold
Brush with the texture, not against it
Brush in one direction, following the grain or texture of the hold, not back and forth like you're scrubbing a pan. Scrubbing back and forth grinds chalk deeper into the pores and can wear soft rock faster. One firm pass with the texture lifts the chalk off and carries it away. A few short, deliberate strokes beat a frantic scrub every time.
When to brush
- Between attempts on a hard move, especially anything crimpy or sloped where friction decides the send.
- Before you start, if the holds are caked from previous climbers.
- At the end of your session outdoors, to reset the rock for the next party.
Let the rock dry
If a hold is damp, don't brush it hard and don't climb on it. Wet rock is softer and a lot more prone to breaking, and brushing a wet hold just smears the chalk into mud. Wait for it to dry. This matters most on sandstone, which can stay fragile for a day or more after rain. When in doubt, leave it alone.
Bristle types
Boar bristle: the gold standard
Boar's hair (natural bristle) is the standard for a reason. It's stiff enough to clear chalk and rubber but soft enough that it won't polish or scratch the rock. For outdoor climbing, boar bristle is what you want. The Sesh Bouldering Chalk Brush uses boar bristle for exactly that.
Nylon: fine for the gym
Nylon bristles are firmer and more durable. They're fine on plastic gym holds, which are tougher than rock and don't care about polishing. Plenty of climbers keep a nylon brush for the gym and a boar brush for outside.
Never use a wire or metal brush on real rock
This is the one hard rule. A steel or wire brush strips chalk fast, sure, but it polishes and gouges the rock surface, permanently. It destroys the exact texture you're trying to clean and ruins the hold for everyone after you. Wire brushes have no place on natural rock. Ever.
Toothbrushes are too small to be useful
A toothbrush gets recommended as a budget option, but it's too small to do real work. The head covers almost no surface area, and the bristles are too soft to move packed-in chalk. Use a real climbing hold brush. It's a cheap piece of gear that lasts.
Brush sizes
Match the brush to the hold. A compact brush gets into small edges, pockets, and crimps where a wide head can't reach, and it clips onto a harness or rides in a pocket. The Sesh Climbing Chalk Brush is built compact for exactly that. Slopers, big features, and gym volumes have a lot of surface area, so a wide bouldering brush covers them in a few passes instead of twenty. Most climbers end up carrying both.
The other size problem is reach. An extension brush for climbing holds is a brush head on a telescoping pole, and on tall boulders and routes it's the only way to clean the upper holds from the ground. Any slim-handled brush lashes to a painter's pole in a pinch, which is the cheap version of the same tool.
A brush you can't reach is a brush you won't use. A chalk bucket with dedicated brush slots keeps both sizes in reach while you climb. The Bolder Chalk Bucket has slots built for that, and the best chalk bucket guide covers what else separates a good bucket from a bag that tips over.
Outdoor etiquette: leave no trace
Brushing outdoors isn't only about friction. It's about access. Climbers keep crags open by being good guests, and visible chalk is one of the most common gripes land managers have. It's cost climbers access at more than one area. Before you walk away from a boulder or a route:
- Brush the excess chalk off the holds. Knock the heavy buildup down so the next person isn't staring at a white smear.
- Brush off your tick marks. Those chalk arrows you drew to find holds are yours to erase. Take them with you.
- Use a soft brush and a light touch. You're removing chalk, not sanding the rock.
Two minutes of brushing at the end of a session keeps the rock looking like rock. The next climber shouldn't be able to tell you were there.
FAQ
How often should I brush climbing holds? Brush between attempts on hard moves where friction matters, and brush off caked holds before you start. Outdoors, always brush off excess chalk and tick marks before you leave. For easy terrain you're flowing through, you don't need to brush every hold.
Can I use a wire brush to clean climbing holds? No. Never use a wire or metal brush on real rock. It polishes and gouges the surface permanently, wrecking the texture and ruining the hold for everyone after you.
What is the best bristle for a climbing brush? Boar bristle (natural hair) is the gold standard. It's stiff enough to clear chalk and rubber but soft enough that it won't damage rock. Nylon is firmer and fine for plastic gym holds, but for outdoor rock, use boar bristle.
Should I brush with or against the texture? Brush in one direction, with the texture or grain of the hold, using a few firm strokes. Scrubbing back and forth grinds chalk deeper into the pores and wears soft rock faster.
Why does brushing a hold actually help? Holds grip because the surface is rough at a microscopic scale. Chalk, rubber, skin, and dirt fill that texture and smooth it out, which kills friction. Brushing clears the gunk so the surface bites again. A clean hold can feel a full grade easier than a dirty one.
Is a toothbrush good enough for climbing? Not really. A toothbrush head is too small to cover real surface area, and the bristles are too soft to move packed-in chalk. A proper climbing brush is cheap, lasts a long time, and does the job in a fraction of the time.
A good brush is a few bucks of gear that makes every hold grip better and keeps the rock clean for the next party. The Sesh Bouldering Chalk Brush is boar bristle for outdoor rock, and the Sesh Climbing Chalk Brush is the compact one for crimps and easy carrying. Keep one in your chalk bucket and actually use it.