Many years ago; a couple of years after WWII my uncle operated a company that made, among other things, a type of heating mat.
In simple terms it was some sort of mixture of non combustible filler mixed with carbon. The amounts of carbon were varied depending on the length, the width, voltage and current necessary to produce a certain amount of heat (wattage).
Electrical connections were made by spraying conducting metal (zinc/ copper/aluminum) across the ends and attaching wires.
There were no actual wires embedded in the mat itself. It was the whole material of the mat that conducted and heated up.
The heating mats could be shaped and then encased in non conducting material. For example one small heater was curved (about six inches in diam.) and was used to ensure that something projecting through the skin of the ill fated Comet jet liners did not freeze and could still be rotated.
Other sizes could be made to several square feet.
With today's interest in electrical heating etc. the product might be of interest?
I've been asking senior relatives from that side of family but no answers.
Anybody got any info/comment? The plant was located in Essex at or near Harlow............ Epping.
terry