Ask a Curator Time – Insulator from Knob and Tube Wiring

This week’s Ask a Curator object is an insulator from knob and tube wiring. Look at the insulator at the top of this photo from Wikipedia (below left) – notice any similarities between this one and the one we found in the Fort McHenry collection (below right)? 

(Photo courtesy of Laura Scudder)(NPS Photo)


 What is Knob and Tube Wiring?

Knob and tube wiring was an early method of electrical wiring, used from c. 1880-1930. Porcelain insulating tubes were used to safely pass a single-insulated copper conductor through joist and stud holes. Porcelain knob insulators were used to support the wires as they ran alongside the beams/walls/etc. Finally, a loom, a flexible cloth insulating sleeve, was used where the conductors entered a wiring device or the wall.  

The insulator we have is an example of a tube.

What other examples of early electrical wiring can you find archeologically?


About Megan L.

Megan graduated from Boston University in 2008 with an M.A. in Historical Archaeology. While in graduate school, she wrote her master's thesis on 18th-century glass drinkingware excavated during the Big Dig and interned with NMSC for 2 years. Megan has been a full-time employee since February 2010.
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