The chemicals for colouring the cellulose materials and the buffers for spectral evaluation (sodium bicarbonate, sodium hydroxide, concentrated sulphuric acid, sodium dihydrogen phosphate, sodium sulfate and hydrochloric acid, all of analytical reagent grade) as well as the inert dye disodium 1-amino-9,10-dioxo-4-[3-(2-sulfonatooxyethylsulfonyl)anilino]anthracene-2-sulfonate a.k.a. Reactive Blue 19 a.k.a. Remazol Brilliant Blue R (RBBR) were from Aldrich (Austria). The pH indicator dyes 2-fluoro-4-[4-(2-hydroxyethanesulfonyl)-phenylazo]-6-methoxyphenol (GJM-492) and 4-[4-(2-hydroxyethanesulfonyl)-phenylazo]-2,6-dimethylphenol (GJM-503) [12] were from Joanneum Research Forschungsgesellschaft mbH. The cellulose sheets Innovia 25 NP with a nominal thickness of 25 μm were from Innovia Films (Germany) and were kindly provided by Joachim Janz. The cotton T-shirts were from adshirt.de (Germany). The cotton facecloth W Vienna Style Supersoft was from Vossen GmbH & Co. KG (Austria). The non-sterile cotton swabs EH11.1 were from Carl Roth GmbH & Co. KG (Germany). The repeated washings of the facecloth were performed in a Bauknecht Dynamic Sense WAK7778 laundry machine (Germany) using 40° and 60 °C programmes and each time approx. 50 ml of the washing agent Splendid Compact Color Universal Laundry Detergent from Spar (Austria) produced by the mibelle group (Switzerland).