For best results, all surfaces need to be thoroughly sanded. This will provide a key for the new paint as well as enhancing the appearance.
Bare wood and plaster should be dry sanded. This produces a lot of dust and a suitable protective mask should always be worn.
Old paintwork can be prepared in the same way but it is also possible to use ‘wet or dry’ paper.
With old paintwork bear in mind that it may contain lead. If in doubt use the wet technique to avoid generating lead dust. Simple kits are available to test for lead content.
Select a suitable grade of paper:
For rough surfaces use "coarse" paper (60 or 80 grade).
For general preparation use "medium" paper (120 grade).
For sanding between coats use "fine" paper (180 grade) and wipe the surface with a tack rag to remove all traces of dust.
The best type of abrasive paper is silicon carbide or aluminium oxide. These materials stay ‘sharper’ longer than conventional papers, cut the surface much more quickly and don’t clog so easily – cheaper in the long run.
On flat surfaces, always wrap the paper around a sanding block (either cork or rubber). This keeps the paper flat and in contact with the surface. It also prevents your fingers becoming sore and helps even sanding.
On wood, always sand with the grain rather than across it.