Silicone grease is a waterproof grease made by combining a silicone oil with a thickener. Most commonly, the silicone oil is polydimethylsiloxane (PDMS) and the thickener is amorphous fumed silica. Using this formulation, silicone grease is a translucent white viscous paste, with exact properties dependent on the type and proportion of the components. More specialized silicone greases are made from fluorinated silicones or, for low temperature applications, PDMS containing some phenyl substituents in place of methyl groups. For food applications, the thickener is calcium stearate. For applications involving highly reactive substances, powdered Teflon is the thickener.