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 from becoming sore and helps even sanding.
On wood, always sand with the grain rather than across it.
Painted surfaces are more quickly rubbed down using a wet technique. The cutting power is governed by the material used to manufacture the sandpaper.
Wrap the wet or dry paper around a rubber block, dip in a bucket of water and sand in the normal way. While working, regularly rinse the paper and always keep it wet.
The water acts like a lubricant, enabling the paper to travel over the surface easily. It also holds the paper firmly in contact with the surface.
With a little practice, this type of sanding produces high quality results.
On broad areas, a slight overlapping circular motion can be used.
Narrower areas and mouldings should be sanded lengthways.
Recesses in mouldings can be sanded using a small folded piece of sandpaper, which can be pushed up and down along the groove. Alternatively, for extra control, fold the paper over the end of a scraper.
The surface should be rinsed afterwards using clean water and a sponge. Allow to dry before repainting.
Cut standard size paper widthways in half for cork blocks, and into quarters for rubber blocks.
Always wear a mask to protect against dust. Check that the mask you buy gives protection against the type of dust being produced.