 |
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
TOPIC: 22. PAINTING
INTRODUCTION; This topic teaches students why painting is necessary; different types of paints; various types of finishes; choosing right colours; different methods paint can be applied; tools and other materials; how a surface is prepared for painting; the process of painting; points to consider in order to get a perfect finish and cleaning of painting equipments.
OBJECTIVES:
22.1. To know the reasons why surfaces have to be painted and to be able to define the terms: waterbased paints and oilbased paints.
22.2. To distinguish between the different finishes and describe them.
22.3. To chose the right colour and to be able to order paints in a clear specification.
22.4. To know the different methods paint can be applied and to be able to use them correctly.
22.5. To name other tools used when doing paint work and to state their uses.
22.6. To be able to prepare a surface by punching nails, puttying holes and sanding the surface smooth.
22.7., 22.8. To be able to surface correctly and produce a perfect finish.
22.9. To clean equipment and working area of paint.
METHOD: This topic is best taught by demonstrating It on a paint project. But as such projects are not always available try to give as much information and hints as possible in the classroom and prepare all paint equipment and different paints and varnishes for the lesson to achieve the best teaching results
Students copy all informations from the blackboard in their trade theory book.
NOTE: At the end of this section three worksheets are prepared to reinforce this topic. Worksheets are corrected and assessed later.
There are two reasons for painting timber - to protect it and to enhance its appearance. Many types of paint are available from different manufactures - Dulux, Taubmans etc. Any colour can be obtained.
a) Waterbased paints: - This paint has water as its base. That means that water makes the paint fluid. When applied, in the process of drying, the water evaporates and only the colour with the other chemicals remains on the surface which is painted.
It is easy to use and handle and equipment is easily cleaned while paint is still wet.
Waterbased paints are also called "Acrylic Paints".
b) Oilbased paints: - This paint has turpentine as base. These "Alkyd Paints" need more care in use and handling but the finish is generally harder than acrylic paints.
In this group we can include wood stain, varnishes, paints etc.
NOTE: For best results select the same type of undercoat and topcoat!
Most topcoat paints and varnishes are available in different degrees of "SHEEN" (light reflection)
a) Matt or Flat: - No shine at all.
b) Semi-gloss or Satin: - Gives a more reflective surface.
c) Full-gloss or High-gloss: - Gives a shiny surface. An advantage is that the surface is easy to keep clean.
There are ready mixed paints available in popular colours. Most dealers have mixing systems where paints can be mixed according to colour charts. These charts are used to identify colours by name or code-numbers. When using the colours for a building you must choose a balanced range of colours. Too many colours makes it expensive (too many left overs). Too few colours makes it boring to look at. Avoid large areas of dark colours in small rooms.
When ordering paint, you must specify the following:
|
a) Manufacturer |
- eg. Taubmans |
|
b) Type of paint |
- eg. Waterbased |
|
c) Sheen |
- eg. Satin |
|
d) Colour |
- eg. Sky blue |
|
e) Size of container |
- eg. 4 litres |
|
f) Quantity |
- eg. 6 Tins |
a) Spraying: - This gives the best result, but it Is difficult to do on building site. Therefore it is best suited for use in spray rooms. Compressed air or electric systems are used.
Figure
b) Roller: - This gives a very attractive surface and it is a very fast and efficient method of applying paint on large surfaces (walls, ceilings). Rollers are available in different sizes and a special tray is used for the paint.
Figure
c) Brush: - For all painting where spraying and rolling is not possible. Brushes are available in different sizes from 12 mm up to 150 mm and in various qualities. Always use a brush which does not lose its bristles.
Figure
Many tools and materials exist to make the work easy and give good results. They include:
a) Putty knives:
Figure
b) Sanding blocks:
Figure
c) Scrapers:
Figure
d) Sandpaper:
Figure
e) Sanding machines:
Figure
f) Fillers, Putties:
Figure
a) NEW SURFACES: It is very important that the work to be painted or varnished is well prepared. No amount of paint can cover up poorly prepared surface.
The first step is to remove cutter marks from timber and even the surface roughly with a plane or heavy sander.
Next, all gaps and nailholes are filled with an appropriate filler. Polly-filla is available for internal and external use and plastic wood with the colour of the timber for varnished surfaces. When the filler is dry it is sanded (except elastic sealants) flush with the work and sharp edges are broken. If a lot of sanding is needed, start with a coarse grit sandpaper and finish with a fine one.
"SAND ONLY ALONG THE GRAIN OF TIMBER TO BE VARNISHED"
Finally all dust is removed.
b) PREVIOUSLY PAINTED SURFACES: If the old paint is damaged or cracked, it is best to remove it completely by scraping or sanding.
If the old paint is ok, it should be cleaned to remove all grease and dirt. It may be necessary to sand it with a fine grit sandpaper. Where necessary gaps must be filled and sanded. Finally all dust is removed.
a) Priming: - First coat to be applied to seal the pores of the timber and prevent following coats to be absorbed. When dry, this coat is sanded to remove raised grains and dust which have settled in the wet paint.
b) Undercoat: - The second coat is the special undercoat which helps to cover the grains. The undercoat, which is normally white, should be tinted when a dark topcoat is applied. The actual topcoat can be used for this. Sand when dry.
c) Topcoat: - One coat of the topcoat is applied to give the final finish and colour. If two coats are applied, sanding in between is necessary.
d) Varnishing: - Varnish is applied in two coats. No undercoat is applied. Sanding is done in between. Usually varnish is applied with a brush. On larger surfaces you can use a roller, but only on semi-gloss or flat varnish. Never on high-gloss varnish!
NOTE: Read instructions on tin before starting.
a) Make sure preparations are in order.
b) Avoid dust. After sweeping and dusting, you must wait until the dust in the air settles before painting, especially with the last topcoat.
c) Start with the upper surface (ceiling, barge etc..) and work your way down.
d) Finish a small area at the time, working the paint in all directions but finish in "one" direction. Whether you use brush or roller start high and work down.
e) Use a brush in corners etc. before rolling.
f) Work quickly (not hastily) to ensure invisible overlaps. Use joints, corners etc. for work stoppages.
g) Do not paint while other work is being carried out in the same room. The fresh paint might be spoiled.
h) Protect sinks, shower tray, cistern, taps, bench tops etc. from droplets of paint with paper or plastic.
i) Remove cupboard and doorhandles and knobs before painting starts. Replace when last topcoat is dry.
j) Prevent deep marks on floor by placing paint tins, turps, putty etc. on a sheet of plastic or paper.
Keep tools (brushes, roller) clean. Tools used with acrylic paint are cleaned in water before paint dries.
If they have been used in alkyd paint, clean them up in turps (kerosene). Remove as much paint as possible from your tools before cleaning.
THE IMPRESSION OF A BUILDING IS ONLY AS GOOD AS THE PAINTWORK.
 |
 |
