2. • Oil have following properties
1. Oils are fats but fats are not oils
2. Oil are generally in liquid form, odourless, tasteless
3. Oil is lighter than water, floats on water
4. greasy to the touch, and have lubricating properties
5. not readily volatile; and may be burned without leaving any residue, i.e., ash.
6. As the temperature increases, surface tension decreases, and spreading rate
increases
7. Oils are extracted from seeds
8. Generally non edible oils are used in paints
3. Difference Between fats and Oil
Fats Oil
Remains solid at room temperature Remains liquid at room
temperature
Relatively more saturated Relatively more unsaturated
Relatively higher melting point Low melting point
More stable Less stable
4. Physical properties are checked as
general routine tests.
• a) Colour : colour as it can influence the
colour of varnish in which it may be
Incorporated
• b) Specific Gravity : The specific gravity
is of the drying oils all Falls within a
narrow range generally between 0.925
to 0.933. The bodied oil are little higher.
it is determined by usual methods using
hydrometer or specific gravity bottle
5. • Properties
c) Refractive Index : Refractive
power of an oil is an important in respect
of his relationship with the refractive index
of the pigments which are dispersed in it.
• Abbe refractometer is used to determine
• Drying oil range of the refractive
indices is comparatively
low from 1.46 to 1.54
6. Properties of Oil
d) Viscosity : The viscosity of an oil is a
measure of the oil’s resistance to
shear. Viscosity is more commonly
known as resistance to flow.
High viscosity implies a high
resistance to flow while a low viscosity
indicates a low resistance to flow
Changes with temperature, decreasing
temperature increases viscosity or vice
versa
7. PROPERTIES
e) Odour : Drying oil possess characteristics odour which are more pronounced in the raw
than refined oil
f)Pour Point : Temperature at which the oil becomes “plastic” and will not flow. Overrides the
effects of viscosity and surface tension. Lighter oils with low viscosities have lower pour
points
g) Drying Time : When the solvents (think turpentine and the modern substitutes for it) in the
oil paint oxidize, it leaves the surface of the painting dry to the touch. It can take as little as
24 hours and as long as 12 days for oil paints to dry.
8. Chemical Properties of Oil
Chemical properties of oil : Chemical properties are
checked as tests.
• a) Acid Value : The amount of free organic acid in an oil
is important in many applications and is express as the
number milligrams of potassium hydroxide required to
neutralize the acid in one gram of oil.
• b) Saponification Value : Define as number of milligrams
of potassium hydroxide required to saponify one
milligram of oil
• c) Iodine Value : The weight of Iodine (in grams)
required per 100 grams of oil is known as iodine value.
Low iodine value indicates a poor quality oil
9. Chemical properties are checked as tests.
d)Acetyl Value : Define as number of milligrams of potassium
hydroxide required to neutralize the acetic acid produced by
saponification of one gram of the acetyl compound.
e) Hydroxyl Value : Define as number of milligrams of potassium
hydroxide equivalent to the acetic acid which combined with 1
gram of the hydroxyl-containing oil
f) Flash Point : Temperature at which an oils vapours will ignite
