Figure 1 shows the results of silica gel granulometry measurements. The material studied has an average particle size of 220 nm. The specific mass of the dry silica gel (xerogel) was 2756 kg/m3. It is important to note that the sample was not mechanically ground, but instead was manually ground in a porcelain mortar with a rubber tipped pestle to break up the biggest lumps. Therefore, it would not be possible to reproduce the granulometry of particles contained in the gel.