The application of ultrasounds (US) in dyeing and washing at industrial scale has become an important research topic in the recent years, as this technology appears to have a high potential to reduce the environmental impact of textile productions, as well as to increase the effectiveness of these basic operations. As far as dyeing is concerned, several studies [1, 2] indicate the possibility to operate at a temperature lower than the one typically suggested, yet achieving excellent dye exhaustion, apparently comparable to those obtained in conventional processes. Natural fibres (wool, cotton and silk) seem to be the most suitable materials for USintensified dyeing, since it is not necessary to exceed the glass transition temperature of the constituent polymers, as the dyestuff diffusion within the fibre matrix is a combined effect of hygroscopic pore swelling and US promoted cavitation. Usually, dye-bath exhaustion given by spectrophotometric analysis in the visible range, is one of the promptest parameters to monitor dyeing with time. However in our US-assisted tests, we noticed that this method provided questionable results by varying the operation parameters, namely temperature. In US-assisted dyeing, cavitation phenomena reduce the interphase mass transfer resistance, thus promoting dyestuff adsorption on the fibre surface. In the subsequent rinsing steps, variable amounts of dyestuff leave the textile substrate due to penetration deficiency. For this reason, a new method aimed at determining correctly the dye uptake was based on DMSO (dimethyl sulfoxide) extractions, either after dyeing or rinsing. By comparing the extracted amount, the quantity of adsorbed dyestuff was determined, thus highlighting the mass transfer intensification due to US effec
