Fig. 10
From: Nano-materials enhanced protectants for natural stone surfaces
Optical photos of Marble (a–c), Qingshi (d–f) and Hedishi (g–l) surfaces. For each set of stone surfaces, left to right, they are blank, treated by nano SiO2 dispersions (1.0 mg/mL for Marbel and Qingshi, 1.5 mg/mL for Hedishi) and nano Al2O3 dispersions (1.0 mg/mL for Marbel and Hedishi, 1.5 mg/mL for Qingshi) in 101S, respectively