Disclosed are a method and a sieve system for screening material. The sieve system (100) comprises a sieve (112) for screening material by selectively passing first particles (30) of the material and not passing second particles (26) of the material based on respective dimensions of the first and second particles relative to dimensions of screening apertures in the sieve (112), a holding container (140) for feeding material to be screened to the sieve (112), and a fines container (150) for receiving the first particles screened by the sieve (112). The method comprises measuring a first fines container load at a first time, measuring a second fines container load at a second time, determining a fines rate by determining a rate of change of the fines container load based on the measured first and second fines container loads and the first and second times, and determining an operating condition of the sieve system (100) based on the determined fines rate. The operating condition may provide an indication that the operation of the sieve (112), another component, or the sieve system (100) as a whole is acceptable or unacceptable.