PAINTING

PAINTING

•Protect the surface of wood,

metal and all structures from

atmospheric influences.

•Prevent decay in wood

•Prevent corrosion in metal

•Provides clean ,smooth and

colored surface

Ingredients of paintBase- solid matter

• Bases-White lead, red lead, oxides of zinc,

antimony white

Liquid vehicle

• carries the solid matter

• Acts as binding material

• Vehicles- linseed oil, Tung oil, stand oil, nut oil

Additives Pigments- coloring agentThinning agents- reducing consistency of

paint- turpentine oilDriers- property of quick drying- cobalt, lead,

manganeseFunction- to absorb oxygen from the

atmosphere and transfer it to

linseed oil for hardening.Inert filler/Adulterant-

improving the durability

- Barium sulphate

Characteristics of good paint• Good spreading power

• Dry quickly

• Durable, tough, resistant to wear on drying

• Color should not fade or change

• Should work smoothly and freely

• Become dry within 9 hours

• Not crack on drying

• Smooth and pleasing appearance.

Type of paints

• Enamel paint

• Emulsion paint

• Distempering

(water paint)

Enamel paint

• It Consists of white lead or zinc white,oil,petroleum,

spirit and resinous matter.

• Dries slowly and forms a hard durable surface

• Not affected by gases,acids,alkalies,hot water and cold

water, steam and temperature.

• Used for external and internal walls.

• Before applying paint, One coat titanium white in pale

linseed oil is applied

Emulsion paint• It contains binding material like polyvinyl acetate and

synthetic resins

• For long life-two coats of emulsion is applied

• Apply a coat of cement paint before applying emulsion

Advantages

• Easy to apply and dry within two hours

• Long lasting paint with no change in color

• Possible to clean the surface with water

• Possess good weather resistance and alkali resistance

Distempering• Water paint

• Prepared by mixing powdered chalk(white) and glue, boiled in

water

• Earthly pigments- umber, Indian red and lamb black –give color

shade

• Powder or paste form- mixed with hot water to form viscous fluid

• Distemper is porous

• Allow water vapor to escape

• less durable.

• Use- to give smooth outer surface in low cost

Preparation of different surfaces for painting

• Painting on new wood work

• Painting on old wood work

• Painting new iron and steel work

• Painting old iron and steel work

• Painting plastered surfaces

Painting on new wood work• Moisture content of timber must be less

than 15% of their dryweight

• Four coats of paints are required

• Before Prime coat

Wood work to be cleaned thoroughly

Nail holes and cracks to be filled with

putty

Rub the surface with water proof

abrasive paper.

• Prime coat

• Pores get filled and opaque covering formed

over the whole surface.

• First coat

• Surface is rubbed with pumic stone- stopping

Each coat applied only after previous coat has

dried completely

Repainting on old wood work

• Old paint should be completely removed

• Removing old paint

– Equal parts of washing soda and quick lime- mixture is

brought to a paste form by adding water

– It is applied on the surface and kept for one hour, then

washed off with water

• After, wood surface is painted as that for new wood

work.

Painting new iron and steel work• Clean the surface by scrapping/brushing

with steel wire brushes

• Phosphoric acid is used to remove the

scale deposit on surface.

• Prime coat is applied using brush

• Two or more coats with a brush /spray

gun

• Each coat applied only after previous coat

has dried completely

Repainting old iron and steel work

• Before repainting, it should be thoroughly washed with

soap water

• If grease is present it may be removed by lime water.

• Remove old paint by flat oxy-acetylene flame over the

metal and then scrapped the surface with wire brush.

• Washed with solution of caustic soda and slaked lime.

Painting plastered surface

• For newly plastered wall, there is considerable amount of

moisture.

• For applying paint wait for at least 3to 6 months.

• Defects in plastered surfaces are to be removed.

• Coats of alkali resistant primer paint should then be applied

on the surface.

• Usual paints:- cement paint, silicate paint, emulsion paint

Thank you