Porcelain Tube House Wiring Insulators

Knob and Tube wiring was used when electrical wiring was first introduced into residential buildings.  This was typically two wire pairs (hot & neutral) with open or lightly insulated wiring.  The wires typically mounted onto split knobs that had a nail or screw to clamp the wire between the two porcelain sections.  The tube insulators were inserted into holes drilled into joists & studs with the wire feeding through the center.  Most tube insulators are not glazed but there are versions with white (clear) and brown glazes.  There is currently no numbering system in the hobby for tube insulators.

Shown are six different tube insulators.  Many have the makers marking incused or embossed into the porcelain.  The six shown here are not glazed, but these do come in white & brown glazes.

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