The preparation required will depend upon the condition of the surface. If it is clean, dry, and sound it will require no special preparation. However, if the surface is powdery or there is other evidence of old distemper residue, it should be dusted off and sealed with stabilising solution.
Distemper is a water based paint that primarily comprises a white base pigment (generally water-soaked whiting, i.e. pulverised chalk) bound with glue. Soft distemper was a common internal finish before the advent of emulsion following the Second World War. Although lime wash was still used indoors, soft distemper seemingly increased in popularity during the Industrial Revolution. Even where a more expensive oil paint scheme was to be executed, new lime plaster surfaces would be temporarily distempered and left one or two years until they had cured. Soft distemper can also be found on lining paper, timber, brick, stone and modern emulsion. It is not dusty if applied correctly, but is unsuitable for highly trafficked or damp areas (cellars, bathrooms etc).
Generally found in older properties and used commonly up to the 20th century before more commercial easy to produce paints such as vinyl and acrylic arrived. Distemper is easily identified. It is soft and dusty to touch and will come off the surface of walls onto your hands. The down side to this surface coating is that nothing will stick to it which is a major problem when you want to redecorate with either wallpaper or paint.
There are several ways this can be done, either by scrubbing with hot water or, the best way, which is to soften it and scrape it off.
Another way is by coating it with wallpaper paste until it can soak up no more. Leave it for ten minutes and add some more. Leave for a further ten minutes then start to scrape off with a normal paint scraper.
Sealing is also an option for distemper but the surface must be completely washed down with hot water to remove all of the dusty, loose particles. You can then use PVA or sealer and there are also other proprietary sealers that can be bought from any DIY store.
Modern paints cope surprisingly well when painted over a small amount of dirt; it is however, far better to wash down with sugar soap first. All paintwork should be washed with sugar soap before repainting. Sugar soap may be bought in powder or concentrated liquid form. This should be dissolved in water first before use.
Gouges or small indents can be filled without further preparation.
Cracks and larger defects will need a little more prep work.
Mix the filler into an easily workable paste. Using an old cup or container is a lot easier then mixing on a flat board. You can go down the easier route ofready mixed filler, which can be bought at any DIY store.
Smooth Use a sanding block to lightly sand the surface flush.Wear a mask when sanding to prevent inhalation of the dust.
When filling cracks at internal angles or at the junction between skirting’s/door frames and walls, use flexible acrylic filler. This will allow for a little movement. It is applied using a mastic gun. You don’t have to be terribly neat as it is water-soluble before it dries and can be simply smoothed using a wet finger or sponge.