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