A ‘vehicle’ is a liquid substance which keeps the ingredients of a paint in liquid suspension. The vehicle is a principal liquid ingredient of a paint and performs the following functions:

The vehicles that are commonly used in all oil paint are briefly described below:

(i) Linseed Oil: This is most commonly used as a vehicle in oil paints. It is obtained from flax seeds. Linseed oil, when exposed to air, gets oxidized and becomes thick. A good quality linseed oil is clear, pale, transparent, brilliant, odourless and sweet in taste. Linseed oil is used in raw, boiled or double boiled forms, as described below:

(a) Raw Linseed Oil: It is thin, odourless, transparent and brilliant. It takes long time for drying. It is used for delicate tints and interior painting work.

(b) Boiled Linseed Oil (or Drying Oil): It is obtained by boiling the oil alone or with drier, viz., red lead, litharge, etc. It is thicker and darker in colour than raw linseed oil. It dries rapidly but has less elasticlty and penetration power than raw linseed oil. It is used for external work. It is not suitable for indoor work of delicate nature.

(c) Pale Boiled Linseed Oil: It is similar to boiled linseed oil except that it is not dark in colour. It is more suitable for painting plastered or metal surfaces.

(d) Double Boiled Linseed Oil: It dries very quickly. It has the same colour and transparency as raw linseed oil but odour is different. It is suitable for painting external work. However, it requires a thinning agent like turpentine.

(ii) Tung Oil: This is much superior to linseed oil and is used in making superior paints and varnishes.
(iii) Poppy Oil: This is obtained by pressing common poppy seeds. It has slow drying qualities but its colour lasts longer than linseed oil. It is expensive and hence is used for making paints of very delicate (light) colours of internal painting.

(iv) Nut Oil: This is extracted from ordinary walnuts. It has rapid drying qualities but is less durable. It is colourless and cheap. It is used for making white and light coloured paints for ordinary works.