Filtering (filtering) is the separation of liquid or gas from suspended solids in the process of passing them through a porous material called filters. This solid particles are trapped on the filter (pore size of the filter is less than the size of particles). The liquid that has passed through the filter, called the filtrate. In labs material for filter is a filter (not glued) a security which is issued by the industry three degrees of porosity: grade B (the largest pores), a brand With (average pore diameter) and mark M (most small pores). Liquid, corrosive filter paper, filtered through glass wool or through a special glass filters.