Evaluation of microscopy techniques and ATR-FTIR spectroscopy on textile fibers from the Vesuvian area: A pilot study on degradation processes that prevent the characterization of bast fibers

Differentiating between Natural and Modified Cellulosic Fibres Using ATR-FTIR Spectroscopy

“…In fact, the percentage lignin content is much lower than for hemp and jute, while hemicellulose content is quite higher [2,5,6,50]. However, ATR-FTIR limitations in differentiating bast fibres cannot be ignored [33]. As proof, in Figure 5, we report spectra of different historical samples of flax which were previously identified by SEM observations (not shown).…”

“…When the fibres need to be clearly identified, several methods can be used [31,32]. Microscopy has traditionally been used to differentiate fibres, using light microscopy (LM) [33,34], polarised light microscopy [12,33,35], and scanning electron microscopy (SEM) [33,34,36,37]. While for cotton, for example, the identification is quite simple, some fibres can be easily confused due to the high natural variability of descriptive parameters.…”

“…Today, Raman [34,39] and FTIR spectroscopy [34,[40][41][42][43] are established techniques to identify the nature of the fibres, both cellulosic and proteinaceous, generally coupled with SEM observation. In particular, ATR-FTIR spectroscopy is used to give chemical information about archaeological textiles, whose morphology is often very decayed due to the biological attack [33,40,41,[44][45][46]. ATR-FTIR analysis permits also to detect a small amount [15] of dyes, mordants, contaminants, and dirt [47,48] such as gypsum, kaolin, and various organic materials which can adhere to historical textiles [45] and papers [49].…”

“…Generally speaking, FTIR can distinguish fibres from different herbaceous plants too, but problems arise when bast fibres are aged [33]. Garside's study [50] on flax, hemp, jute, ramie, cotton, and sisal proposed the use of two ratios based on the intensities of infrared bands representing the overall organic content (2900 cm −1 ), lignin content (1595 cm −1 ), and cellulose content (1105 cm −1 ).…”

“…Although the technique also obtains indications of the total cellulose crystallinity of the material [52], data collection and interpretation are more complicated than the non-polarised ATR-FTIR mode. Similarly, good results are obtained when ATR-FTIR data are processed with the chemometrics method in order to cluster fresh fibres from different sources [33,53]. However, the best performances are obtained when advanced chemometric methods are applied [54].…”