Weight accurately about 5g. of organic or 10g. inorganic pigment. The
sample is placed on a glass or marble plate. Linseed oil ( Acid Refined
Linseed oil conforming to IS :75-1973 having an acid value equal to 4-8)
is then added slowly, 4 to 5 deops at a time from burette & rubbed
into pigment with palette knife. This addition is continued until agglomerates
of oil and pigment are formed and form this point, oil is added only
one drop at a time followed by a thorough rubbing with a papalette knife.
The paste will be such that it will just sparead without craking or curmbling.
By nothing the quantity of oil used, the oil absorption value is calculated
and expressed as the greams of oil required 100g. of pigment.
BLEEDING IN SOLVENTS
Weight 0.5g. of pigment and 20ml of solvent in aconcial flask. Shake
for 30 min. on a flask shaker.Filter the contents through whatman No.44
filter with Blanc Fixe bed. Observe the colour of filtrate and assess
the dgree of bleeding on 1 to 5 scale.
Scale -1 Considerable bleeding Scale-5 No bleeding
REDISTANCE TO ACID & ALKALI
Stir 10g. of pigment and 500ml of HCL or NaOH ( 5% in case of
organic and 1% in case of inorganic pigment ) in beaker for 1 hour. Filter
and wash with water till Ph is neutral. Dry in an ovan, Mill and mix
together with varnish on muller. Assess the shade difference on draw
down between treated and untreated sample on 1 to 5 scale by using blue
Scale 1- Considerable discolouration Scale 5- No discolouration.
Specific Gravity is tested as per IS : 3493-1978 (Method of
sampling and test for Organic pigment for paints)
Weight an empty specific gravity bottle with lid (w1). fill with Kerosene
and put the stopper and take weight (a). Again fill with water and put
the stopper and take the weight. In a clean bottle weight 1-2g. of sample
and weigh along with the lid (W2). Fill the bottle to 1/4th layer above
the pigment with kerosene and place in a deciccator
with lid. Connect to. The vacuum for 2 hrs. Take the bottle from deciccator
and fill it completely with kerosene and weigh alongwith a stopper (c).
Specified gravity = b * s / (a+b)-c
b=W2 - W1=Weight of the pigment
s=Specific gravity of the Kerosene
a=Weight of the bottle+kerosene
c=Weigh of bottle + Kerosene + sample
Fastness to heat
The maximum processing temperature is given based on 5 minutes exposure
in an injection moulder cavity.
Fastness to Mirgration
Full shade PVC Sheet is placed between 2 pieces of white
flexible PVC Sheets under a weight of 100g/cm for 1 hour at 120
Migration is assessed on 1 to 5 scale.
Scale 1 - Heavy migration Scale 5- No migration
pH OF PIGMENT POWDER
Weight 10g. pigment in a 250 ml. beaker, add 5 ml. Of deionized
water to wet the pigment. Make a paste with a glass road. Add 150ml.
deionized water and boil for 5 minutes. Coll the mixture to room temperature.
Filter through Whatman n o.5. Make the volume of filtrate to 250ml. in
volumetric flask. Check the pH of filreate using glass and refence electrode.
MATTER SOLUBLE IN WATER (W.S)
Water soluble is tested as per IS : 3439-1978 ( Method
of sampling and test for organic pigments for paints ). Weight
5g. of pigment. Add 10ml. of methanol and make a paste. add about
200 ml. of water and boil for 5 minutes. Cool
to room temperature. Transfer it to 250ml. volumetric flask through
blanc fixe bed. Take 100ml. of filtrate in a previously weighed
150 ml.beaker (W1). Evaporate the solution on a hot plate till
dryness. Keep the beaker in an oven at 102+- 2'C for 1 hour.Cool
in the desiccator to room temperature and reweigh the beaker
Water soluble matter = (W1-W2) * 250 / Wt. of the sample.
Volatile matter is tested as per IS : 3493-1978 ( Mathod of
sampling and test Organic pigment for paints) Weigh a clean, dry Petri-dish
accurately on a balance (W1). Take 2-3g. sample in a weighed dish and
reweighed it (W2). Keep it open in an oven in an oven at 102+/ C for
2 hrs. Cool in the desiccator and weigh it (W3).Repeat the procedure
of drying , cooling and weighing till constant weigh is obtained.
%Volatile matter = (W2 - W3) * 100 / (W2- W1)
About 10g. of orgainc pigment or 30 g. of inorgainic pigment
is accurately weighed and transferred into a 50 ml. measuring cylinder.
The cylinder is then fixed on Bulk Density apparatus and 50 strokes are
given to the cylinder. Volume is noted. Bulk Density is expressed as
the grams of the material per cc of its volume.
FASTNESS TO LIGHT
Depending on the major wnd application the product is
recommended for i.e. paint, printing, inks, plastics, the light
fastness is checked for that end application. The exhibits are
exposed in QUV Accelerated weathering Tester and light fastness
is assessed on 1 to 8 8 scale.
Scale 1- poor light Fatness Scale 8- Excellent light Fastness
PAINTS & COATINGS
Fastness to heat
Indicates the maximum recommended temperature, based on 20 minutes
stoving in oven.
Fastness to overspray
Overspray the full shade specimen with white stoving
enamel.Stove at 130° C for 20 minutes. Assess the degree
of bleeding on 1 to 5 scale.
Scale 1 - Heavy bleeding Scale 5 - No bleeding