Thursday, November 1, 2012

Insulator Post -- Hemingray Drip Points


It's November and I've got insulators on my mind.  This weekend the big 42nd annual Mid-Ohio Insulator Show is held in Springfield and I'll be making the trek down to gaze upon a multitude of colorful glass.  Hopefully I'll find a couple nice California's for my collection.

In this installment we'll take a look at an interesting but obscure corner of the antique glass insulator world; the drip point.  Drip points always come up in conversations when I run into non-collectors who show me that one old Hemingray insulator they had laying around out in the barn or on a windowsill.  Not too many people know the purpose of the little teeth ringing the bottoms of these common insulators except collectors inclined enough to poke around and learn the history.  I always get a kick out of explaining this little piece of Hemingray lore when I have a chance.

In the latter half of the 19th century entrepreneurship was booming. Inventors, businessmen and industrialists were forging ahead at full steam each trying to outdo his competitors in the new and growing industrial based economy of a young America.  The story of the drip point is right out of that era. 
Patent drawing courtesy of Christian E. Willis' most excellent website:

A hundred years ago the telecommunication industry and the then infantile power distribution systems of our country were at the mercy of the weather just like they are today.  The purpose of the insulator was to isolate the telegraph and telephone wires from the support structures thus preserving the circuit allowing signals to travel the system and provide communication between distant points.

Water is an excellent conductor of electricity and with every rain shower comes the risk of a film of moisture creating a short circuit and allowing the voltage a quick and easy path to ground down the pole instead of staying along the copper carrying out its intended task.

The drip point was Ralph Hemingray and J.C. Gill's innovative idea to help rain water shed off the glass insulator.  I've included the patent application letter below and it is interesting to read the reasoning behind the little "teats" as they were called by the inventors themselves.

All of the insulators photographed are from my personal collection.  This trio of Hemingray insulators are still stained with carbon soot from their time spent in close proximity to a steam powered railroad line.  Some collectors like to clean the insulators of this black residue but I don't touch them.  I think the soot adds unique character to the piece; A telltale clue of the insulator's actual use during a bygone era.

Here's a nice double groove pony with drip points a co-worker found for me at a flea market for fifty cents.  The May 2 1893 embossing signifies the patent date not the date the insulator was produced.  This particular piece was probably made at some point in the twenty or so years after the original patent was issued.

As is often the case time is not kind to the brittle glass teeth and they become chipped.  Rare indeed is the specimen with all its drips intact and fanatical collectors seek them out spending years trading up until they find that prized piece in mint condition.
               UNITED STATES PATENT 
                            Application filed January 3, 1893. Serial No. 457,057. (No model.)
To all whom it may concern:
Be it known that we, RALPH G. HEMIN-GRAY of Covington, county of Kenton, State of Kentucky, and JAMES C. GILL, of Muncie, county of Delaware, State of Indiana, citizens of the United States, have invented certain new and useful Improvements in Insulators for Telegraph-Wires and the Like, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings, forming part of this specification.
Our improvements relate to insulators in which means are devised to obtain as perfect insulation as possible, and to prevent the water which collects on the insulator during rains, from effecting the insulation, by coating the surface of the insulator and thus forming connection between the wire and the insulator support.
In the drawings: - Figure 1 is a side elevation of our improved insulator. Fig. 2, is a central vertical section of the same.
A, is the body of the insulator made of glass, porcelain or other suitable insulating material.
B, is the usual groove for the tie-wire, by which the main wire is secured to the insulator. The insulator is molded with a screw threaded recess C in the usual way, by means of which the insulator is secured to its support. The insulator shown is further provided with what is known as a "double petticoat," which consists of the inner shield D and the outer shield E, with the recess a, between the two shields or "petticoats." This double shield or double petticoat arrangement, has been long in use, to present a broad weather protected surface between the lower outer edge of the insulator and the support, the idea being to obtain such abroad surface that water running down the outside of the insulator, will not be able to find
its way to the supporting peg.
It is to obtain a more perfect insulation than has been obtained by this arrangement, that our invention is directed. To accomplish this result, we mold or secure at the lower edge of the flaring bell-mouth of the insulator, a series of lugs or teats b, b. These teats are arranged in series around the lower edge of the insulator and preferably so close together, as to attract and receive on their rounded points, all drops of water that may run down the sides of the insulator. With this construction the teats b attract and draw to their points, where they drop off one at a time, all drops of water which would otherwise gradually extend themselves by capillary attraction over the inner surface of the insulator. We find in practice that a single row of these teats arranged on the lower edge of the insulator, is sufficient, but when desired, of course the inner shield D could be provided with a similar series of teats.
Of course we do not wish to be limited to the particular class of "double petticoat" insulators shown in the drawings, as our series of teats can be formed on the lower edge of any of the well known forms of insulators.
Having thus described our invention, what we claim, and desire to secure by Letters Patent, is -
An insulator, provided with a series of teats at the lower edge of the insulator shield, to attract and gather at their points the drops of water running down the outer surface of the insulator, substantially as described.



Eventually Hemingray transitioned into using round drip points as shown on this hoop skirt.  By the 1950's the drip point was already fading off into obscurity as glass fell out of favor and porcelain took over as the material of choice for insulation duty.
Drip points are a favorite topic among Hemingray collectors.  The argument can surely be made that drip points were just a gimmick, a way for Hemingray to differentiate his product from his  competitors. Which is the way I tend to lean when contemplating the subject.  I even read once of one motivated collector who set up a test with insulators with smooth bases side by side with drip point equipped versions and as far as he could tell there was no difference in the ability of water to remove itself from the bottom of the glass.


  1. Interesting. I had wondered about this before, but never long enough to research it.

  2. Thanks Nate, Always cool to teach some history to a teacher!

    A few other companies incorporated drip points into their molds once the patent expired.

    Personally I like smooth base insulators like the Californias. It's hard enough to find a pristine piece of glass over 100 years old let alone find one with all those tiny points still attached.

  3. From personal experience, I can assure you that not all those drip points were intact up on the poles. My guess is that they frequently were chipped or fell off before they ever even went up.

  4. Yes I agree Nate. Packaging and shipping methods were pretty crude in those days so probably lots of broken teeth before they even made it out to the field.