It was the inherent dangers of these open wound coils in either firebrick or porcelain holders that caused the European nations to mandate the cast iron elements with which research and progress stalled for decades. Of course, in this country, research continued and Hotpoint engineers developed the sealed rod element which enclosed the open wound coil in a stainless steel tube. The open coil was insulated electrically with magnesium oxide and improvements were continuous. The magnesium oxide insulation is why there is the bright yellow light when a sealed rod element shorts internally. Hotpoint's discovery led to General Electric's purchasing the company to get the Calrod element which is why you see the note in Hotpoint ads of old that it was a subsidiary of the General Electric Co.
One nice thing about the old open coil elements sunk into channels in the firebrick or porcelain holders was that the intense heat of the element did not touch the pan so Pyrex and other brands of heatproof glass cooking vessels could be used without danger of thermal destruction on the elements. The sealed rod elements, unless used on slower speeds, had to have the wire used between them and the glass vessel to prevent breakage from thermal shock due to the fact that glass does not transmit heat very well from a place of high heat to a place of lower heat. Another nice thing about the open coil elements was that the firebrick absorbed a LOT of heat, which was not good for efficiency in the initial heating, but could be used to cook with the current off. When we were using a hotplate to cook in lodgings, I remember my mother using the percolator on it. She brought the water to perking on high then she shut if off and there was enough heat to perk the coffee for 8 minutes or so. Early marketing of electrical cooking used to emphasize the savings to be had of cooking while the current was off. The European cast iron elements held even more heat.
(50 Year Repair Tech Beltsville,Md) 
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