In high temperature processes like incineration, gasification or pyrolysis of biomass and waste, the long-term stable filtration performance is drastically reduced due to a significant fraction of sticky particulates. Especially in these processes, the fly ashes can already soften at temperatures below 400 degrees C. In consequence, filter clogging is enhanced and regeneration is hindered. For the evaluation of the filtration performance and for the adjustment of the recleaning parameters, the analysis of the temperature-dependent adhesion characteristics of fly ashes and dusts is essential. Conventional shear cells, however, usually require precompressing of the samples and will be operated intermittent at one temperature per sample. A continuous measurement of highly porous dusts is not possible. Therefore, a rotational rheometer was developed, which permits - in a temperature range up to 1300 degrees C - conclusions on the height of the effective adhesive forces. Continuously measured variable is the torque of a slowly rotating stirrer, which results from the relocation and displacement of particles and/or agglomerates in a non-compacted powder and correlates directly with the current adhesion characteristics. On the basis of model dusts the advantages and possibilities of the measuring method are pointed out and apparatus- as well as material-related relevant parameters will be discussed. (C) 2007 Elsevier B.V. All rights reserved.