Table 6.

Ratio between the values of stain discolouration D* of Apuan marble and Ajarte samples treated the nanocomposites WNC and ANC and with Silres BS 290 (D*Silres).

	Apuan Marble		Ajarte
Time (min.)	D*WNC/D*Silres	D*ANC/D*Silres	D*WNC/D*Silres	D*ANC/D*Silres
30	2.16	0.71	5.64	0.15
40	1.86	0.75	6.40	1.14
90	1.58	0.76	3.90	1.95
150	1.34	1.30	3.31	2.00