Painting ~ the main objectives of applying coats of paint to a
surface are preservation, protection and decoration to give a
finish which is easy to clean and maintain. To achieve these
objectives the surface preparation and paint application must be
adequate. The preparation of new and previously painted surfaces
should ensure that prior to painting the surface is smooth, clean,
dry and stable.Basic Surface Preparation Techniques ~Timber † to ensure a good adhesion of the paint film all timber
should have a moisture content of less than 18%. The timber
surface should be prepared using an abrasive paper to produce a
smooth surface brushed and wiped free of dust and any grease
removed with a suitable spirit. Careful treatment of knots is
essential either by sealing with two coats of knotting or in
extreme cases cutting out the knot and replacing with sound
timber. The stopping and filling of cracks and fixing holes with
putty or an appropriate filler should be carried out after the
application of the priming coat. Each coat of paint must be
allowed to dry hard and be rubbed down with a fine abrasive paper
before applying the next coat. On previously painted surfaces if
the paint is in a reasonable condition the surface will only require
cleaning and rubbing down before repainting, when the paint is in a
poor condition it will be necessary to remove completely the
layers of paint and then prepare the surface as described above
for new timber.Building Boards † most of these boards require no special
preparation except for the application of a sealer as specified by
the manufacturer.Iron and Steel † good preparation is the key to painting iron and
steel successfully and this will include removing all rust, mill scale,
oil, grease and wax. This can be achieved by wire brushing, using
mechanical means such as shot blasting, flame cleaning and
chemical processes and any of these processes are often carried
out in the steel fabrication works prior to shop applied priming.Plaster † the essential requirement of the preparation is to ensure
that the plaster surface is perfectly dry, smooth and free of
defects before applying any coats of paint especially when using
gloss paints. Plaster which contains lime can be alkaline and such
surfaces should be treated with an alkali resistant primer when the
surface is dry before applying the final coats of paint.Painting---Preparation