nonconductor

On this point he remarks that the evil effects of the scale are due to the fact that it is relatively a nonconductor of heat.

Paper can be so treated that it will either conduct electricity or become a nonconductor, as may be desired.

Strictly speaking, all substances conduct electricity in some degree, and a nonconductor is merely a bad conductor.

All you have to do is wrap your core with a nonconductor, say nylon thread, and presto, nothing comes out.