Weigh 10 grams of pigment (2 grams if it is carbon black) on an industrial balance and put it on a sieve. The number of holes in this sieve should meet the requirements of the technical conditions. The festival of the pigment is carried out by hand shaking method or mechanical vibration method. When the sieve is shaken on the smooth paper for half a minute, and no pigment particles are found falling on the paper through the sieve holes, the sieve can be stopped. Use a large brush to sweep up the remaining pigment on the knot and put it on the watch glass and weigh it.
The residue on the node can be expressed as a percentage according to the following formula:
X=100(b/a)
Among them: X: % of the residue on the sieve; a is the grams of the total weight of the pigment pattern; b is the grams of the pigment residue that passes through the sieve.
If the maximum sieved amount is taken as 100%, the difference between the two measurements shall not exceed 10%.
Take about 10 grams of pigment (2 grams when using carbon black) and 250 milliliters of water to reconcile in a porcelain dish. Gently grind the residue at the bottom of the dish with your fingers, and at the same time pour the suspension several times on the sieve surface (the number of holes of which is specified in the corresponding standard) that has been wetted with water. When all the clumps have been ground up, collect the residue on the sieve. Put the sieve surface with the pigment in a container filled with 250ml of water, and use a soft brush to grind on the sieve surface. The water in the dish was changed several times until there was no trace of pigment in it. First wet the residue with ethanol, then wet it with a centrifuge, and place it in the air for 30 minutes, then put it in a drying box (oven) and dry it at 100~105°C until it reaches a constant weight. The residue on the sieve is expressed as a percentage according to the previous formula.
In the case of pigments that are soluble in water, tests shall be carried out with other wetting liquids (for example, gasoline) that do not dissolve the pigment.
If the number of grams of the maximum sieved amount is taken as 100%, the difference between the two determinations shall not exceed 5%.
Determining the degree of dispersion of the same pigment in different laboratories often yields different results. This is because the tests were carried out in different ways. Therefore one should always use a method that gives exactly the same result, and use a fixed method that is strictly consistent with previous records.