Filter sheets are made in the same way as paper, i.e. by wet laying, but they are both thicker than paper and rougher in texture. They have traditionally been used in forms of filter presses and employed to clarify beverages such as beer and whisky or to sterilize pharmaceutical solutions. An array of filter sheets is shown in Figure 2.2. These sheets closely resemble thick filter paper and, in fact, were originally made from a mixture of cellulose and asbestos fibres; recent years have seen asbestos displaced, because of its health hazards, by kieselguhr. Because of the importance of the polishing duties performed by the sheet filter, the cellulose-based sheet is now being replaced by membrane filters.
For further information, please click here.