A unique contact probe/thermocouple has been built for studying characteristics of small patches of solid-to-solid contact at the sealing interface of mechanical face seals during seal operation. The probe was used to determine the number, size, location, and surface temperature of contact patches over a range of seal velocities. Both dry and liquid-lubricated conditions were studied, and three different metallic seal ring materials were tested. It was found that small, discrete contact patches are, indeed, present on the contact interface, that the patches tend to be stationary with respect to the metallic seal ring, whether that ring is stationary or rotating, and that the size and temperature of the contact spots are influenced by operating velocity and by the thermal, elastic, and wear properties of the seal materials.Presented at the 38th Annual Meeting in Houston, Texas, April 24–28, 1983