Hot plate and sample temperature curves

The hot plate and sample block heat up at different rates because heat must diffuse from the hot plate into the block. Heating in the block lags behind that of the hot plate, exceeding an 80°C lag after a 2 hour heating cycle to a hot plate temperature of 220°C. The hot plate-sample block temperature differential decreases and equilibrates at ~60°C less than the 220°C hot plate. This experiment was performed with the hood on, sash open, with no Teflon jacket.

Dots are equilibrium temperatures of hot plate and sample block under different conditions. The heating block follows the hot plate temperature along the red curve below (hood on, no Teflon jacket) or the green curve (hood off, Teflon jacket in place). With the hood off and jacket on, a 180°C sample block temperature requires a 225°C hot plate temperature (green line).