The
physical, chemical, colouristic as well fastness properties
of the pigments depend to a large extent on the type of
binders used, presence of extenders, driers, hardness, the
substrate and film thickness etc. The data offered therefore
is only as a general guidance.
Physical
Properties
Specific
Gravity: Specific gravity has been determined in
an inert liquid at 20 C.
Oil Absorption: 10 gm. of pigment is placed
on a glass plate and acid refind linseed oil is added from
a burrette in drops, and the paste rubbed to get a spreadable
paste. The quantity of oil required for 100 gms. of Pigment
is then calculated and expressed as ml. oil/100 grams Pigment.
Light Fastness: The prints of the pigment
dispersed in printing ink medium is exposed along with Standard
Blue Scale and rating expressed in 1 to 8 scale. 8 denotes
excellence and 1 denoting poor tastness.
Heat Resistance: A stoving paint of the
Pigment is prepared in non yellowing medium and applied
to a tin panel. The temperature upto which there is negligible
change in the shade after stoving for 30 minutes is noted.
Fastness to solvents and chemicals: The
test is carried out by placing 0.5 gms. of pigment in a
folded paper, sealed at the top and suspended in 20 cc.
of solvent in a stoppered test tube at room temperature
for 24 hours. The staining noted and expressed in 1 to 5
scale.
In case of water, acid or alkali: 0.5 gm.
of pigment is mixed with 10 ml. each & these liquids
heated in a water bath for 10 mts. cooled and filtered.
The filterate is assessed for colouration.
Soap bleeding: The test is carried out
by placing completely dried draw-down/print on 20% Jelly
made with neutral white Soap for 24 hours. Extent of bleeding
noted and expressed in 1 to 5 scale.
