Faults in Old Paint Surfaces
There are several faults that appear in old paint surfaces. These include crazing, mould, cracks, flaking, blistering and bubbling, as well as the normal dents and chips of everyday wear.
Chips can be rectified by first removing the old paint, rubbing down or ‘feathering’ with glass paper and filling the hole with a cellulose. A hard-stopper would be used for external use, applied after the primer coat, and a soft-stopper used internally. This is allowed to harden and then rubbed down and primed.
When one coat of paint is applied over a coat of an entirely differently constituted paint the result may be crazing. The new and original coats of paint contract at different rates. If badly crazed, the entire surface must be stripped back to the bare wood which should be knotted and primed before painting. Small areas may be locally treated by rubbing down with a wet-and-dry paper before applying a new top coat.
A small area of blistering may be treated, by lifting the eruption with a knife, knotting the cavity, priming, filling with stopper and allowing to dry before rubbing down level with the surrounding surface. Once the surface has been allowed to dry the repaired areas can be primed.
Cracks in ceilings, walls and plaster according to size can be filled with plaster or cellulose. Make sure the crack to be filled is clean, clear out loose material and cut back if needed. Cracks should be dusted and damped before filling. Press the filler in and smooth off with a knife. Sand down to achieve a smooth surface.
If the plaster surface is to be painted it is a good idea to add a little of the chosen colour to the filler. This helps the filled area to blend under the colour coat.
Very wide or deep cracks should be cleared out and filled in layers, allowing each layer to dry before putting in the next.
Efflorescence, or the permeation of alkaline salts through the plaster, can only be cured if the wall is allowed to dry out. Use an alkaline-resistant primer and then redecorate.
Mould should be scraped off before redecorating. This can be caused by damp and lack of ventilation. Wash down with an anti-fungicidal preparation, allow to dry and then redecorate.
Primer and undercoating fulfil two functions: primer is used to seal a new or newly prepared surface; it is used on unpainted surfaces. Undercoat is used to fill in the wood before the top coats are added.
The finished effect in painting can only be as good as the work of preparation which went into it. Time spent in preparing the work and the careful choice of materials and ‘tools’, may possibly seem tedious but should enable you to achieve results of which you may be justly proud.