Keying and painting a radiator

Turn off the heating and let the radiator cool down, cover the floor and wall, and remove dust and grease thoroughly. Paint only adheres to a clean, matt surface.

Sand rusty spots back to bare metal with P120 and feather the edges into the intact paint with P180. Only matt down the remaining paint: with P240 or abrasive fleece, which can be worked into curves and between the fins.

A small random orbital sander can help on flat surfaces; fins, ribs and edges by hand – there the machine only presses dents or sands through the edges.

Treat bare spots immediately with an anti-rust primer, then apply a heat-resistant radiator paint as directed by the manufacturer. Only turn the heating back on once it has fully dried.

Where neither machine nor sanding block can reach, a strip of abrasive fleece or sandpaper does the job: wrap it round a flat ruler, or hold both ends like a shoe-shine cloth and pull it back and forth. You are only matting – the paint should be dull, not removed.

Very old radiators may have lead-based paint. If in doubt, do not dry sand – work wet with abrasive fleece and wear a mask (FFP3). In any case: vacuum the dust rather than sweeping it, and wipe down with a slightly damp cloth before painting.