Filtration is a separation technique that is used to separate a solid that has not dissolved in a liquid (for example a precipitate). A filter paper is placed inside a glass funnel and a container put beneath. The mixture of the solid and liquid is placed into the filter paper.The liquid flows through the filter paper and in to the container. The liquid in the container is called the filtrate. The solid that remains in the filter paper is called the residue.The residue can be dried by spreading it out on the filter paper and allowing the liquid to evaporate.he liquid flows through the filter paper and in to the container. The liquid in the container is called the filtrate. The solid that remains in the filter paper is called the residue.