Combination of a Green and a Traditional Method for Estimating Relative and Absolute Ink Age: A Case Study of Ballpoint Pen Ink Dating in Vietnam

Table 2

HPTLC R_f values of A3.1, A3.2, and M1 samples developed in solvent system B (from left to right in Figure 5).

N o	Spot	R f of A3.1	R f of A3.2 (39 months)	R f of M1 (50 months)	Color under visible light	Remark
1	a	0.74	0.72	0.71	Violet	Color intensity and Rf value: A3.1 > A3.2 > M1
2	b	0.80	0.78	0.76	Violet
3	c	0.85	0.84	0.83	Violet
4	d	0.95	0.94	0.93	Yellow