How to distinguish good quality pigment paste for coatings industry?

So many water based pigment paste suppliers in the market, the auxiliaries in pigment paste formulation are many and complex. Some of pigment pastes have more water and less pigment contented, and pigment powder quality also affects the colors of water based pigment paste. When the coatings formulation engineers are facing a large number of pigment paste products, they can use three methods to test and evaluate one of good pigment paste:  

1. Scratching pigment paste on fineness board. Generally, fineness board is widely used in water based coatings, solvent based coatings and ink industry, to detect the water based pigment paste fineness.

 1). Wipe the fineness plate carefully with soft wiping cloth and make it clean;

 2).Scraper contacts the surface of clean fineness board vertically;

 3).The angle between checking sight line and fineness board should be 15 to 30 degree; measurement of coating fineness would be tested three times in the same way, and then gets the arithmetic average of two testing results which is similar readings in three readings. The error of two reading values should not be more than the minimum scale of instrument. Fineness board as shown below:  the pigment paste fineness particle is between 25-30μ.

2. Comparative of coloring strength 

Coloring strength testing is to detect the differences of pigment paste in coloring strength and hue. Weight a certain number grams of coatings, such as 50grams (picture shown), put 1-2 grams pigment paste into and stirring evenly according to this ratio. Then using a film coater coat and checking.

The film coater is shown below, with different thickness indicated; you can coat films with different thickness.

3. Finger testing research

Put a certain number grams of water based pigment paste into resin used in coatings,  coat as film on the glass board or white card paper, then lightly make finger testing when the film is semi-dry, until the surface of film is nearly full dry. Observe and measure color changes between finger test area and other area. This is to test the compatibility of pigment paste. If it is poor, the colors wil be different, shown as below black coating.

The above three ways, we can use this pigment paste for coating formulation if it has good fineness, strong coloring power and good compatibility. 

水性色浆