Arctic Silver 5 High-Density Polysynthetic Silver Thermal Compound is a stable, electrical insulator with controlled triple-phase viscosity that contains 99.9% pure silver. Due to the unique shape and sizes of the particles in Arctic Silver 5's conductive matrix, it will take up to 200 hours and several thermal cycles to achieve maximum particle to particle thermal conduction and for the heatsink to CPU interface to reach maximum conductivity. (This period will be longer in a system without a fan on the heatsink or with a low speed fax on the heatsink.) On systems measuring actual internal core temperatures via the CPU's internal diode, the measured temperature will often drop 2'C to 5'C over this break-in period. This break-in will occur during the normal use of the computer as long as the computer is turned off from time to time and the interface is allowed to cool to room temperature. Once the break-in is complete, the computer can be left on if desired.