Abstract <p>The article considers methodological aspects of using compacts (pressed samples) to study surface tension, wetting, and a number of other important colloidal-chemical properties of polymineral powders, including those subjected to mechanical activation. The effect of changes occurring with materials during pressing is investigated, and recommendations are developed for making pressed samples to measure surface tension. Compacts from mechanically activated quartz-containing polymineral powder of varying degrees of dispersion were made by pressing under pressure from 15.9 to 707.4 MPa. Surface tension (polar and dispersion components), color coordinates, and strength properties were determined for the samples obtained. It is shown that there are functional dependences between the characteristics under consideration and the duration of grinding, as well as the pressing pressure. For the first time, the nature of changes in the polar component of the surface tension of mineral powders during their mechanical activation and pressing (compact production) was established. A feature of pressing finely dispersed powders has been revealed, consisting in a decrease in the values of the surface tension indicator (due to a denser packing of particles in samples and, as a result, the formation of a large number of van der Waals bonds), while for coarsely dispersed powders an increase in its values is observed due to the crushing of brittle grains of minerals and, as a result, the formation of new active centers occurs. On the basis of the determination of the surface tension of mineral powder systems using compacts, recommendations have been developed for their manufacture to avoid possible errors in measuring the surface tension of the original mineral powders.</p>