A detailed Guide for Painting House or Office building for Engineers & Home-Owners:

First Step is preparation of the surface to be painted.

The Various precautions and procedure to follow has been provided below:

 

1. PREPARATION OF SURFACE

• General

All surfaces specified to be painted shall be dry and cleaned free of all dirt, grit, grease, mold, oil, mildew, foreign substances and all loose, peeling, blistering, chalking or scaling paint.

Before starting the work Site-Engineer/Home-Owner shall inspect soundness and readiness of the surface to be painted on.

 

1.2 Preparation of Masonry, Concrete and Plastered Surface

Preparation work like masonry work, crack filling, water proofing etc. should be preferably done before commencing actual painting work.This is also necessary to get the maximum life of the final paint film by doing proper planning for color scheme and selection of brushes/rollers.

 

1.2.1 In case of New Plaster Surface

 

Ensure Surface Dryness

If possible, the plastered surface should be left unpainted for the first few months to allow it to carbonate, harden and dry thoroughly. If not possible to leave the plaster bare, a temporary decoration of soft distemper (non-washable) or a coat of lime may be applied

No attempt should be made to apply solvent based paint (especially gloss finishes) until the plastered surfaces of new brickwork, concrete or building blocks are thoroughly dry.

 

Cleaning & Treatment

Before painting, the surface should be thoroughly brushed to remove all dirt and remains of loose or powered materials to provide a mechanical key between surface and paint for satisfactory adhesion.

Treatment of the surface with solution of acids or salts such as zinc sulphate is not advisable as the risk of alkali attack is not reduced appreciably and efflorescence may be increased.

 

1.2.2  In case of Old Unpainted Plaster Surface

 

Surface Dryness

• Painting should be deferred until the plaster has dried. Any source of dampness in walls and ceilings should be removed.
• Any major cracks or defects in the plaster should be cut out in V shape and made good to avoid undue absorption of water and subsequent shrinkage of the filling.
• Minor repairs may be made with cement mortar. Fine cracks may be primed and subsequently filled with a putty of suitable consistency made out of enamel, water and whiting powder.

 

Cleaning & Treatment

• Any fungus and algae growth must be completely removed by brushing it vigorously with wire brush and by cleaning it with water.
• If there is an extensive growth of vegetable material which cannot be removed by brushing, the growth should be destroyed by applying a wash of ammoniacal copper solution. This treatment should be done with greater care on the top of the awnings, sunshades, parapets and other horizontal surfaces where water is likely to accumulate during monsoon.
• (A recommended composition and concentration of the ammoniacal wash shall consist of 7 g of copper carbonate dissolved in 80 ml liquor ammonia and diluted to one liter with water.)

 

1.2.3  In case of previously painted Plaster Surface

 

Surface Dryness

• Any existing paint showing excessive flaking, bleaching, or saponification (presence of yellow soapy runs) should be removed by scrapping and washing and the surface allowed to dry completely.
• Dry distempers and lime wash should be totally removed prior to repainting. It may sometimes be necessary to wet the surface before scraping. This should not be overdone, and all surfaces should be perfectly dry prior to the application of any priming coats.
• Previously oil painted surfaces should be sanded thoroughly to remove loose particles and made dull and matt for better adhesion.
• Exterior rough surfaces, previously coated with cement paint, should be wire brushed and washed with water thoroughly and allowed drying. Before painting, ensure that the surface is free from chalking.
• The exterior surface should not be affected by any water or by constant dampness.
• In case of painting during the rains, the surface should be allowed to dry out completely for 2-3 days of total sunshine before commencing painting.

 

Cleaning & Treatment

• Any existing fungus or algae growth should be completely removed by scrapping and rubbing down the surface thoroughly with bristle brush and sand paper. The surface should be washed down with clean water and allowed to dry.

• A coat of fungicidal wash should then be applied and allowed to dry after which a further coat should be applied and left for some time to dry thoroughly.
• Local defective patches should be treated individually by removing all loose or softened paint and bringing forward the treated patches with primer and undercoating before applying a fresh coating over the whole area.
• In case of re-painting, previous coating of lime wash or powder distemper must be thoroughly scrapped off.
• The gloss or sheen of coatings of oil or synthetic emulsion paints; if not in good condition, must be removed by thorough sanding.

 

Priming Coat

• Certain wall and ceiling surfaces may reveal hairline cracks. After complete removal of the existing paint systems and if the lime plaster has cured and dried completely, use at least two coats of any of the primers for the paint system to be adopted. When solvent-based paint is to be used, the primer at least shall be of the alkali resistant type. Lime fast pigments shall be used.

• Water based paint or washable distemper, if in a clean, sound condition, need not be removed if similar coatings are to be applied in the new paint system. By using a mild detergent, the surface may be washed and then after a light sanding, will be ready to receive a fresh coat (with spot priming if required).

 

1.3 Preparation of Metal surface

• To be ready for painting, a surface should be clean, dry and sound, and it should, as far as possible, also have reached a stable state.
• Pre-treatment and priming of ferrous and non-ferrous metals under controlled conditions at the factory gives the best results and it is, therefore, advisable to adopt this method whenever possible.
• The single most important factor is the correct surface preparation of the metals prior to the painting, as the presence of rust, oil, grease and dirt under the paint film can cause its failure.
• Therefore, the surface should be clean, dry, free from contaminants and rough enough to ensure adhesion of the paint film. This can be done by any one or a combination of the following methods:

 

Manual hand cleaning

To remove rust, scale or old coatings with the use of emery paper, wire brushes, scrapers etc. for spot cleaning during normal maintenance.

 

Surface washing

To remove salt deposits and grime with lukewarm water containing 1 to 2% detergent. After that the surface is to be dried, lightly wire brushed and sand papered. This is useful where only the finishing coat of paint shows signs of deterioration, and the primary coat of paint is sufficiently in good condition

 

Blast cleaning

To remove rust, mill scale (oxidization) and old paints with the use of high velocity impact of abrasives (sand & grit). It is the most effective method of surface preparation.

 

Cleaning with power driven tools

To remove oil, grease, heavy scale / mill scales, rust / residual rust.

 

Flame cleaning

With the application of an oxy-acetylene flame and then after rust can be removed by wire brushes. However, it should not be done on plates with thickness 10 mm or less.

 

Temporary coatings

When painting cannot immediately follow surface preparation, the temporary coatings will be applied with the use of linseed oil applied uniformly and thinly (one third litre on 10 sqm area) or prefabrication primers.

 

1.4     Preparation of Wood surface

• Wood absorbs moisture so that it must be treated well before application of paint. The wooden surfaces should be inspected for insects and fungus that are generally found in woods which are soft and porous in nature.
• It must be checked that any defects likely to be occurred during surface preparation should be rectified well before commencing the painting work.
• The process of making the surface fit for paint application, in which the surface is made smooth, free of surface imperfections and thoroughly clean of all dust & dirt.

 

1.4.1  For new wood surface

The wood should be well seasoned, dried, and cleaned of scales, smoke and grease and the entire surface shall be sandpapered along the grains to make it smooth. Knots excreting resin in the wood and causing cracking, peeling and brown discoloration shall be treated properly.

 

1.4.2  For old wood surface

• If the old paint is sound and firm and its removal is considered unnecessary, the surface shall be rubbed down with sandpaper to remove all dust and loose paint after it has been cleaned of all smoke and grease.
• If required, grease shall be removed by washing with lime/washing soda and rinsing with water.
• If the old surface is blistered or flaked badly, it should be removed completely with sharp glass piece/stripping knife, sandpaper and by use of either:

Patent paint remover: Remover solution is applied with brush and when the paint film lifts and wrinkles, it is scrapped thoroughly. After removal of paint, surface shall be washed down with turpentine.

Or

Caustic soda solution: (1 part soda + 48 parts water) this is applied with brush and when the paint film lifts and wrinkles, it is scrapped thoroughly. After removal, surface should be rinsed with several change of clean water with little acetic acid/vinegar in final rounds of rinsing.

Or

Blowlamp: Flame is moved over the paint coating just enough to soften it without charring the paint and/or background. The softened paint is removed completely with scrapping knife/glass piece. Burning off shall be carried out from bottom to upward on vertical surface. Blowlamp shall not be used on narrow/carved/undercut surfaces or where there is a risk of damage to adjoining material.