Rub-Out Test | Test Methoden | BYK Additives

In pigment mixtures separation of pigments will occur if the pigments are not properly stabilized. This defect is known as flooding/floating and becomes visible as color change when the rub-out test is performed. Most paints contain more than just one pigment. Pigments in such a pigment mixture will separate when not all of them are properly stabilized by wetting and dispersing additives. Two grey paints (pigmented with carbon black and titanium dioxide) are poured onto a vertical, slightly tilted polyester foil side by side. After a short flash-off time when the paints are still wet the so-called "rub-out" test is performed: the lower part of the paint films is rubbed with a finger. This movement will homogenize the pigment mixture in this area and if any separation had occured during flash-off a color difference will become visible between the rubbed and the non-rubbed area. In our example the rubbed area on the left hand side shows a lighter color than the area above: this indicates that in this paint sample the carbon black was floating to the surface of the paint film due to pigment separation. On the right hand side no color difference is visible: the system is perfectly stabilized with a wetting and dispersing additive and no pigment separation occurs. Learn more about BYK's wetting and dispersing additives: https://www.byk.com/en/additives/prod...