Ceramic filters used to remove particles from hot gases were tested at temperatures between 200 and 850degreesC with redispersed combustion ashes from biomass, two (German) coals, municipal waste as well as mixtures of ash with sorbent particles. The duration of the first 50 filtration cycles was used to derive a measure of operating stability. For the same ash materials, data on thermal expansion (by dilatometry), weight loss (by thermo-gravimetric analysis) and relative heat flux (by differential scanning calorimetry) were obtained. Pure powders of NaHCO3, Ca(OH)(2), CaCO3 and Na2SO4 were tested for comparison. Particle size and chemical composition information for the ashes was also obtained. Filtration behavior correlated with thermo-analytical data for the various materials, in that temperature regions of pronounced physical or chemical changes within the powder samples were generally good indicators of instable filter operation. Materials of complex composition such as ashes and in some cases also the pure powders had more than one region of instability, with 'metastable' filter operation possible in between. A chart was developed to attempt the prediction of mixtures of ashes with pure powders.