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

Table 5

The similar functional groups for the FTIR spectrum of the adhesive sample on the back side of the blue stamp, which turned out to be gum Arabic samples.

Functional group	Wavenumbers (cm^−1)				Characterization
	Standard gum Arabic sample	Gum Arabic reference spectrum	Blue stamp sample	Red stamp sample
O-H stretching band	3200–3600	3313	3281	3335	Characteristic of glycosidic ring
C-H stretching bands	2800–3000	2925	2854–2923	2850–2920	v(C-H) in CH3 pyranose ring
C-H bending bands	1300–1480	1425	1311–1415	1414	Carboxylic groups of uronic acid residues of gum polysaccharides
C-O stretching bands	900–1300	1017	1016	1026	Finger print of carbohydrates or polymer backbone

Data are from previous [89–93]. Pure gum Arabic.