APPLICATIONS AND QUANTITIES
Selecting the correct paint system
The selection of the correct paint to be used on specific substrate (for example, plaster, wood, galvanised steel and so forth) is complicated because of the large number and varieties of coatings available, as well as many different trade names. Before setting out to buy the paint, bear in mind that a paint system normally consists of a primer, an undercoat and a finishing coat.
Once you have established what substrate you are going to deal with, one can decide on the type of finishing coat. Depending on the choice of finishing coat, you may need a particular primer and undercoat.
At this stage you must also give thought to the quality of the paint that you intend buying. It is better to have a long term point of view rather than buying the cheapest paint available.
Remember, penny wise, pound foolish. Your paint stockist should give you professional guidance in selecting the right grade of paint. If they can't, dont buy from them.
Correct quantity of paint
Do not waste money by buying too much paint or risk spoiling the job by buying too little. The first step in estimating the quantity needed is to establish the size of the surface area, for example, measure the length, width and height of the walls, windows and doors. Calculate the total area of walls and subtract total area of windows and doors. For a roof, gutter end and slope must be measured. A correction factor must, however, be introduced for profiled surfaces, e.g. IBR sheeting and corrugated iron, to allow for the extra area created by the profile. Usually, an addition of one third of the area is sufficient.
The second step is to establish the practical spreading rate of the paint to be used, taking into account wastage, variation in surface profile, application technique, absorbency of surface and so forth. A practical spreading rate can be obtained from your local Paint Stockist.
The third and final step is to calculate the quantity of paint required.
Having determined the area and the practical spread rate, the quantity of paint required will be:
Quantity (litres) = Area m2
Practical spreading rate (ms/l)
Correct application method
We must assure ourselves of the correct method of application in terms of:
- The application technique and the equipment top be used, for example, brush, roller or spray.
- The correct drying and overcoating times i.e. the previous coat must be dry before applying the subsequent coat.
- The correct environment conditions. One does not apply paint in cold wet weather or paint a galvanised roof in the heat of the day.
- Take the necessary precaution steps to minimise the mess and spillage we may unavoidably make while stripping, cleaning and painting the surface. Locks, door handles and similar fittings should be removed or masked and refitted when the painting is completed. Also cover carpets, furniture and fittings which cannot be removed. Drop sheets are heavy duty 3 by 2 metre plastic protective cover sheets and are ideal for this purpose.
- Have the correct tools handy for surface preparation (paint scraper, wire brush, putty knife, sandpaper and so forth), application (brush, roller or spray) and cleaning equipment. Brushes should be cleaned with a multi-purpose solvent which may be used repeatably ensuring maximum life for brushes.
- Paint must be thoroughly stirred before use unless other wise stated. Brushes and rollers must be of a suitable quality for the specific paint system to be applied.
Equipment must be cleaned with the appropriate cleaner for each type of paint. Where paint is allowed to age, before finishing, the surface must be prepared by a light sanding followed by dusting and scrubbing with bristle brushes and cleaner and allowed to dry before overcoating. Each coat of paint must be allowed to dry and all dirt and other surface contaminants must be removed before the next coat is applied.