Characterization of Two Historical Postage Stamps Made from Cotton Fibers and Their Restoration Trials Based on the Experimental Studies

Table 2

Raman spectra of the blue stamp components.

Compound	Raman shift/wavenumbers (cm^−1)
	Reference sample	Stamp sample
Ultramarine blue	352, 378, 549	346, 377, 546
Calcium carbonate	283, 713, 1087	280, 712, 1088
Kaolinite	120, 145	121, 147
Flaxseed oil	865, 1076, 1302, 1443	869, 1070, 1307, 1438

Data are from [11, 15, 41].