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

Table 3

Raman spectra from the reference and red stamp samples.

Compound	Raman shift/wavenumbers (cm^-1)
	Reference sample	Stamp sample
Barium sulfate	454, 464, 989	458, 460, 992
Calcium carbonate	283, 713, 1087	1017
Kaolinite (silica)	145	147
Flax seed oil	865, 1076, 1302	864, 1447
Hematite	225, 245, 294, 290–300, 412	295, 227, 412

Data are from [11, 15, 41, 80].