Nineteenth Century Wire Insulation: The Beginning of Wire Insulation

Nineteenth Century Wire Insulation

The history of wire insulation starts in the nineteenth century.

Insulators are in electrical equipment. Also, insulation helps support and separate electrical conductors.

An insulating material that encases electrical cables or other equipment is insulation.

The first electrical systems to make use of insulators were telegraph lines.

This took place in the 1840’s.

Glass served as the primary insulator at the time. Also, plant products worked to wrap cables or hold wires.

In 1844, Samuel F.B. Morse sent the first telegraph message.

Consequently, he used a flat wood board beneath an apparatus as an insulator to hold wires.

Therefore, the wire directly attached to a wooden pole. This delivered very poor results. Especially, during damp weather.

In 1893, Westinghouse developed a transmission line for the famous Niagara Falls to Buffalo transmission.

This had porcelain insulators. However, these insulators were rated at 11,000 volts.

Consequently, they were only temporary.

Therefore, they were only in place until insulator technology was developed that could handle 22,000 volts.

Common Types of Insulation

The most common types of Nineteenth Century Wire Insulation were:

  • Glass
  • Ceramic or Porcelain
  • Also, wax and oil


Glass acts as a conductor when exposed to humidity.

It attracts vapors of the atmosphere to its surface.

They form a thin film of water. This provides a way for the electricity to pass through.

The types of insulators for glass are:

  • Glass unprotected by iron.
  • Along with, glass protected by an iron covering.
  • This is in addition to, pine wood baked and soaked with shellac then having a piece of glass inserted.
  • Also, glazed porous earthenware.
  • Baked clay.
  • Glass upon wooden pins.

This glass is protected by many different materials.

These materials include: a wooden shield, white flint, bone-rubber surrounding an iron hook, as well as the bone-rubber protected by an iron covering.

Objections to Using Glass

However, there is a large objection to the use of the unprotected glass insulator.

Due to its great liability to fracture.

The first glass insulators used in large quantities had an unthreaded pinhole.

These pieces of glass were positioned on a tapered wooden pin.

This pin was vertically extending upwards from the pole’s cross arm.

Consequently, natural contraction and expansion of the wires tied to these “thread-less insulators” often unseating from their pins.

This resulted in manual resetting of the insulators.

The manufacturers of the glass insulator find it extremely difficult to increase the strength of the material by increasing its thickness.

Mainly due to the account of the difficulty experienced in suitable annealing it.

As a result, a slight scratch would often cause the thicker insulator to fracture and become useless.


Porcelain insulators were produced from clay, quartz or alumina and feldspar.

Finally, they were covered with a smooth glaze to shed water.

Insulators made from porcelain rich in alumina are used where high mechanical strength is important.

Demand for master potters dramatically increased to create porcelain products.

This was due to the new electrical revolution of the 1880’s.

Simply changing to existing porcelain products was only a temporary solution.

Especially because, the needs for even higher voltages came about in the 1890’s.

William Cermak Makes History

Chemists and material engineers helped design higher performance porcelain insulators with special coatings and designs.

William Cermak, who came from Kasejovice, Czech, built a reputation for glass and porcelain pottery.

He developed the now famous “petticoated” insulator design. This design offered a succession of ridges.

One of his pioneering designs handled over 10,000 volts for the first time in history.

Wax and Oil:

In the 1880’s, Edison used Trinidad asphaltum with linseed oil, beeswax, and paraffin to insulate copper wires mounted inside of iron pipes.

Mainly used for durable underground power lines.

They were made famous at the Pearl Street Station in NYC.

Insulating Oil (Transformer Oil) – This petroleum product served as an electrical insulator and thermal conductor.

Especially since, it conducts heat away from hot transformer coils.

Also, some capacitors use insulator oil.

Helpful Information

For more information on Falconer Electronics, please click these helpful links:

Finally, to learn about Wire Harness Assemblies, please click below:


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