Just as the sugars found in sap become concentrated during boiling, so too are the naturally occurring minerals found in sap. As the concentration of minerals increases in the sap, it approaches, then exceeds the point of saturation. When that happens, sugar sand which is a precipitate made primarily of calcium, forms and gives syrup a cloudy appearance. Syrup coming directly from the evaporator is therefore cloudy and must be filtered before being stored in a barrel or bottled for consumer use. One way of removing sugar sand from syrup is with a pressure filter. These devices are used in many industries and rely on a pump to force syrup through filter media. The most common filter media is food grade diatomaceous earth (also known as DE). Make sure to follow the recommended guidelines for handling DE. DE is the skeletal remains of single-celled plants called diatoms. These microscopic algae come in many species and differ depending on if they lived in fresh or saltwater. DE appears like a white powder. Under extremely high power magnification, diatoms have many complex shapes, some like sand dollars, baskets or other sieve-like shapes. It is the secondary pores found on each individual DE particle that captures the fine sugar sand and produces a syrup that sparkles.