Which paint brush should I buy for which paint?

The single fact that decides brush choice is that natural bristle is hollow and absorbs water. Put a natural-bristle brush into emulsion and the bristles swell, go limp and splay, and the brush stops holding an edge within minutes. Synthetic filaments do not absorb water, which is why they took over as water-based paints did. Everything else about brush choice is secondary to getting that right.

Step by step

1. Match the filament to the paint's carrier.Water-based paint — emulsion, acrylic satinwood and gloss, water-based varnish, water-based woodstain — needs synthetic filament, usually a nylon and polyester blend. Solvent-based paint — traditional oil gloss, oil undercoat, oil varnish, white-spirit-borne stains — works best with natural bristle, which holds more paint and lays off beautifully.
2. Buy three sizes, not eight.A 50mm for skirting, architrave, door frames and general trim; a 25mm or 38mm angled brush for cutting in and for glazing bars; a 100mm for large flat areas and fences. Almost every domestic job is covered by those, and one good brush beats four cheap ones.
3. Look at the filament tips, not the handle.A good brush has flagged or tipped ends — the filament tips are split or tapered, which is what lets it hold paint and release it smoothly. A cheap brush has blunt-cut ends, holds less, releases unevenly and leaves ridges. You can see the difference by looking at the tip in the light.
4. Check the thickness and the ferrule.Squeeze the head: a good brush is thick and springy right through, not thin with a wide spacer inside. The ferrule should be firmly crimped with no movement. A brush that flexes at the ferrule will not hold a straight line.
5. Use an angled brush for cutting in.The angled tip lets you present a narrow edge to the line while keeping the body of the brush loaded, which is precisely what freehand cutting in requires. It is the single most useful specialist shape in a domestic kit.
6. Do not use your good brushes for everything.Keep a cheap brush for stain block, shellac, knotting, adhesive, preservative and anything you will not get out again. Shellac in particular ruins a brush unless you clean it in methylated spirit immediately.
7. Clean them properly and they last for years.Water-based out of a synthetic brush comes out in warm soapy water if you do it before it sets, working the paint out of the heel with your fingers. Solvent-based needs white spirit then a wash. Reshape, wrap in the original keeper or a piece of paper, and store hanging or flat, never standing on the bristles.

Tips

• A brush that has dried with paint set in the heel is finished as a finishing brush, however clean the tips look. The heel is where the flex comes from.
• Foam brushes are for varnish and small tidy jobs, not for laying emulsion. They hold very little and collapse.
• For a smooth finish on a flat door, a small foam or microfibre roller followed by very light laying off with a good brush beats a brush alone.

Common mistakes

• Using natural bristle in emulsion — The hollow bristles absorb water, swell and go limp. The brush loses its shape and its edge within a few minutes and never recovers.
• Buying a pack of five cheap brushes for a whole house — They shed hairs into every coat, hold little paint and leave ridged brush marks. Two good brushes cost the same and give a visibly better result.
• Standing a brush in a jar of water or spirit on its bristles — It bends the filaments permanently. Suspend it if you must soak it, or wrap it and use it again within the day.

Questions people ask