Soak
Soak turns up in 2 fields: heat treating, metrology. Here is what it means to the people in each one.
Soak in heat treating
To hold parts at a set temperature until they are evenly heated and the intended change is complete.
Holding a load at temperature after the furnace reaches setpoint, long enough for the core to catch up and for carbon and alloy to go into solution. Soak time depends on section size, load density and grade: plain carbon steels need little, while high-alloy tool steels need time for carbides to dissolve. Too short leaves soft cores; too long wastes furnace time and invites decarburization and grain growth.
"Load's at heat, start the soak clock now, ninety minutes and then drop it."
Soak in metrology
Letting an instrument, artifact or part sit in the lab environment until it reaches thermal equilibrium.
Lab slang for the waiting period that lets an item settle to lab temperature, or an instrument warm up, before it is measured. Gauge blocks and large parts may soak on a granite plate for hours, mass standards are left to equilibrate before weighing, and precision meters and calibrators need a warm-up of an hour or more. Skipping the soak puts unmodeled thermal error into every reading.
"That ring gauge came straight off the truck, let it soak overnight before you touch it."