Depends on if your definition of clean is to render the contaminant inert (which is going to basically always involve some sort of chemical reaction) or to just

Depends on if your definition of clean is to render the contaminant inert (which is going to basically always involve some sort of chemical reaction) or to just move it elsewhere. If you want to wash the problem down the drain then making large clumps out of the offending molecules helps. If you want to actually alter the offending molecules then you'll probably not want something that makes clumps. This is why doctor's wash their hands while janitors wipe down surfaces with disinfectants.