ABOUT INSULATORS

An insulator contains no free electrons to permit the flow of electricity.

When a voltage is placed across an insulator, no charge or current flows through the insulator.

An insulator is intended to support or separate electrical wires without passing current through itself.

The term electrical insulation has the same meaning as the term dielectric.

Some materials such as silicon dioxide or teflon are very good electrical insulators.

A much larger class of materials, for example rubber-like polymers and most plastics are still "good enough" to insulate electrical wiring and cables even though they may have lower bulk resistivity.

These materials can serve as practical and safe insulators for low to moderate voltages (hundreds, or even thousands, of volts).

The History Of Insulators

When Benjamin Franklin flew his famous kite in the thunderstorm in 1752, he used a silk handkerchief as an insulator.

The first electrical systems to make use of insulators were telegraph lines; direct attachment of wires to wooden poles was found to give very poor results, especially during damp weather.

The first glass insulators used en masse had an unthreaded pinhole.

These pieces of glass were positioned on a tapered wooden pin, vertically extending upwards from the pole's crossarm (commonly only two insulators to a pole and maybe one on top of the pole itself).

Natural contraction and expansion of the wires tied to these "threadless insulators" resulted in insulators unseating from their pins, requiring manual reseating.

AN EARLY ENGLISH STONEWARE INSULATOR

Amongst the first to produce ceramic insulators were companies in the United Kingdom, with Stiff and Doulton using stoneware from the mid 1840s, Joseph Bourne (later renamed Denby) producing them from around 1860 and Bullers from 1868.

Besides being beautiful, glass insulators are a fascinating part of our history. The oldest insulators pre-date the Civil War. Some companies, like Hemingray and Brookfield, were around for years and produced many insulators. Others were around much less time. Also, as with many antiques and collectibles, some styles were experimental or only produced in limited quantities, and as a result are far more rare than others. There are many nuances in the styles, uses, colors and uses of glass insulators. It seems each one is an interesting story in itself! 

Utility patent number 48,906 was granted to Louis A. Cauvet on July 25, 1865 for a process to produce insulators with a threaded pinhole. To this day, pin-type insulators still have threaded pinholes.

The invention of suspension-type insulators made high-voltage power transmission possible.

Pin-type insulators were unsatisfactory over about 60,000 volts.

In the late 1960s and early 1970s, glass insulators were being removed from telephone poles as advances in technology made them obsolete. As linemen were taking down the old lines, they started to notice the multitude of bright colors, company names, variety of shapes, and important historical position held by insulators in the expansion of communication technology.

Tumbling Glass Insulators

Insulators that have been buried can take on a frosted appearance.  Others have been scratched or have surface pitting. 

If an insulator is valuable, but not in the best shape, it can be well worth your while to have it tumbled bu a professional. 

There are differences of opinions among experts about tumbling, so be sure and read up on it before you decide. 

In many cases the results are impressive, restoring the shine to the glass and making a piece collector-worthy again 

Presently the glass insulator collecting hobby has attracted thousands of people from around the world.