material is again evident fig8 shows reflection spectra of a moist and a dry polyester fabric which also show differences in their derivative functions fig9 different materials can be separated from one another by spectroscopy in the near infrared range with a main component analysis as known for example from the book u201c erkennen von kunststoffen u2014 qualitative kunststoffanalyse mit einfachen mitteln u201d detecting synthetic materials u2014 qualitative synthetic material analysis by simple means by dietrich braun 1998 3 rd edition this shows that the wavelength range from 1500 nm to 1800 nm is moisture independent fig1 shows reflectance or reflection spectra of nylon 6 and nylon 6 6 which can only be separated from one another in a wavelength range of between 2400 and 2500 nm fig1 and 12 show reflection spectra of rayon and polyacrylonitrile at a reflection of the water band which depends on the moisture content of the fibers the moisture content can be determined by the evaluation circuit 15 fig1 shows an absorption spectrum of polyethylene in the wave number range of from 3500 to 500 cm u2212 1 fig1 shows a reflection spectrum of cotton in the dry and moist states the cotton still having a certain residual dampness when it is in the garment dryer 1 if the spectra for dry cotton is consequently stored in a memory assigned to the evaluation circuit 15 it can be detected from the respectively measured spectrum by comparison with the spectrum for dry cotton whether the drying process must be continued or whether the desired residual dampness for example the ironing.