Tungsten evaporation filaments are made from high purity, minimum 99.95%, refractory metals with high melting points and low vapor pressures. The most commonly used metal are tungsten, molybdenum and tantalum. There are many different evaporation source designs, forms include multi-strand filaments, wire baskets, boats and crucibles.

The tungsten filaments are manufactured from high grade tungsten. Of all metals pure form, tungsten has the highest melting point (3422°C / 6192°F), the lowest vapor pressure at temperatures above 1650°C (3000°F) and has the highest tensile strength. Tungsten also has the lowest coefficient of thermal expansion of any pure metal. This combination of properties makes tungsten the ideal material for evaporation sources.