Coarse fillers will cause titanium dioxide to accumulate together in the dry film of latex paint, thereby reducing its hiding power, while fine fillers can separate titanium dioxide, thereby improving its hiding power. This effect of fine fillers is called spacing, and this kind of fine fillers is called spacing extender or spacer, titanium dioxide spacer, or titanium dioxide diluent. The separation effect can be expressed by the dilution efficiency (Ed) of titanium dioxide. Dilution efficiency is defined as the ratio of the volume of the filler used as a titanium dioxide spacer to the total volume of the filler, see the table for details.
Table 1 Dilution efficiency of fillers with different particle sizes
