The first change from the Heichal et al. design was the addition
of the Teflon coating on the wire, which is simply the standard
insulator sold with the wire (Omega product number TFCI-010-
XX). The Teflon coating was left on as otherwise electrical isolation
between the wire and the substrate could not be achieved consistently
with cement alone. It should be noted that while Teflon’s
melting temperature is 327 C, it is only rated to 260 C and the
thermocouple may not be suitable for temperatures above this.