CHAPTER ONE
INTRODUCTION
Paint is a mixture of insoluble particles of pigment suspended in a continuous organic or aqueous vehicle. It is most commonly used to protect, colour or provide texture to objects. Paint can be made or purchased in many colours and in many different types. It is typically stored, solid, and applied as a liquid, but dries into a solid. With a branch, a roller, or a spray gun, paint is applied in a thin coat to various surfaces such as wood, metal, or stone.
Samples of the first known paintings made between 20,000 and 23,000 years ago, survive in caves in france and spain. Primitive paintings tended to depict humans and animals, and diagrams have also been found. Early artists relied on easily available natural substances to make paint such as natural earth pigments, charcoal, berry juice, blood, lard, and milk-weed sap. Later, the ancient Chinese, Egyptians, Hebrews, Greeks and Romans used more sophisticated materials to produced paints for limited decoration, such as painting walls. Oils were used as vanishes, and pigments such as yellow and red ochres, chalk, arsenic sulfide yellow, and malachite green were mixed with binders such as gun arabic, lime, egg albumen and beeswax.
The twenty-first century has seen the changes in paint composition and manufacture. Today, synthetic pigments and stabilizers are commonly used to mass produce uniform batches of paints. New synthetic vehicle developed from polymers such as polyreuthane and styrene-butadene emerged during the 1940s. Alkyd resins more synthesized, and they have dominated production since. Before 1930, pigment was ground with stone mills, and these were later replaced by steel balls. Today sand mills and high-speed dispersion mixers are used to ground dispersible pigments. Perhaps the greatest paint-related advanced has been its proliferation.
COMPOSITION OF PAINTS
Generally speaking, components of paints can be discussed under the following:
- Pigments
- Binders (Resins)
- Solvents
- Additives
PIGMENTS: Pigment can define as a substance used for colouring (hiding) purpose. However, more technically, pigments can be defined as finely powdered solid substance, essentially insoluble in the medium in which they are dispersed (if any) and are used in paints to provide the dried film and such properties as, hiding and colour. There are different kinds of pigments used in making paints like basic white pigment (titanium dioxide) selected for its excellent concealing properties, black pigments commonly made from carbon black. Others are iron oxide and cadmium sulfide for reds, metallic salts for yellow and oranges, iron blue and chrome yellows for blues and greens.
BINDERS (RESINS): Simplistically, a binder is anything that binds, while technically, a binder is a non volatile portion of the vehicle of a paint, it binds or cement the pigments particles together and also the paint film as a whole to the material it is applied. Examples of binders are thickener (Nitrosol) and Acrylic.
SOLVENTS: solvents are various low viscous, volatile liquids. They aid flow and applicability of the paint products.
Solvents can commonly be divided into two, viz: polar solvents and non polar solvent.
Polar solvents are known to contain OH group (alchanol groups) where as non polar solvents do not contain the OH and are mostly organic in nature. In the surface coating industry, i.e. paint industry, the universal solvent is water. Water is found common and generally used in the water based-paint. In the same way, it can be said that the none polar solvents are used in the oil based paint.
ADDITIVES: Additives are those components of a paint system other than the primary components (pigments, binders, and solvents) which are introduced to serve special purposes.
The purposes of the additives are as follows:
- To facilitate the manufacturing process.
- To enhance the products stability and durability
- To enhance the product performance, which include application and film quality so as to achieve all the desirous goals of the coating.
TYPES OF PAINT
There are many types of paint, which include oil paints, emulsion paints, textured paints (texcote), cellulose paints, bituminous paints and rubber-based paints.
1. OIL PAINTS: Oil paint is a type of slow-drying paint that consists of particles of pigments suspended in a drying oil, commonly linseed oil. The viscosity of the paint may be modified by the addition of a solvent such as turpentine or white spirit, and varnish may be added to increase the glossiness of the dried oil paint film. It is the oldest and most traditional of the types of paint, generally suitable for all surfaces, but not the most economical for all occasions. Oil paints have been used in Europe since the 12th century for simple decoration but were not widely adopted as an artistic medium until the early 15th century. Common modern applications of oil paint are in finishing and protection of wood in buildings and exposed metal structures such as ships and bridges. Its hard-wearing properties and luminous colour make it desirable for both interior and exterior use on wood and metal. Due to its slow-drying properties, it has recently been used in paint- on-glass animation. Thickness of coat has considerable bearing on time required for drying.
