Pilkington Brothers Limited

Go back with me to the Spring of 1976. I am sitting at my insulator "sales table" at our church bazaar here in Houston. On one side of me I see a lady with her table full of dried flower arrangements. On the other side is a table loaded with homemade candy. Both vendors are doing very well, but I am having no luck. People pick up the insulators, make their usual unfunny remark about having shot BB guns at them as youngsters, and then set them down and walk away. Pretty soon Father Bill Tinney walks by, asks me a question or two, and then says, "Don't go away- I'll be right back!"

Minutes later he reappears holding a large glass insulator resembling a "sombrero". Though it is smeared with mud, I can see it is of a light green coke bottle color, has a metal cap on it and a metal thimble inside the pinhole. It seems that it had been partially buried in his back yard, and there are six more besides this one! He asks me if I would like to have it, and when I tell him yes, he confesses that he is addicted to auctions and had attended one in Houston about nine years before where the cargo of a confiscated ship was being auctioned off to the public by U.S. Customs. Not wanting to invest a whole lot of money, but bent on going home with something, he bought the basket of insulators. The price was certainly right -- $.50 for the whole lot! He didn't like them much, but they intrigued him because the story was that they were being shipped to some island in the Caribbean Sea. Soon after he returned home, the novelty of his purchase began to wear off, and he pitched them in his back yard, where they had remained ever since. He made me a gift of all seven. I was thrilled (?) to-death, and he walked away -- exactly 56 pounds lighter! 

Closer examination revealed the word ARMOURLight sandblasted on the glass shed of the insulator, plus a lot of numbers which meant nothing to me. But I referred to N. R. Woodward's book The Glass Insulator in America 1973 Report and found that ARMOURLight is the trademark name for toughened glass insulators made for use on high voltage lines by Pilkington Brothers in England. Though the book is essentially about insulators in America, he has included a brief but interesting story on Pilkington glass. This 1973 Report, by the way is a must for any serious insulator collector. It is packed with valuable information on the C.D. System, includes many, many drawings of insulators, and relates the histories of the various companies that manufactured insulators. 

So .... assuming that the plant at St. Helens, Lancashire, England, was still in operation, we wrote to Pilkington Brothers and requested information on this particular insulator, and also asked them how to successfully remove the metal fittings without breaking the glass. I thought they were ugly! We would like to share with you their reply complete with drawings. (See following pages.)

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Cut all round metal cap about 1/2" from rim with hacksaw (metal saw blade) until you're through to the cement. Then force a chisel of wedge between and the two parts will split away. The cement can then be cleared away.  Note: Ensure that the metal is completely sawn through all round the cap by cutting into the cement. Then take a hammer and knock the cap off. Sharp taps with the hammer on the cap will also dislodge the cement.

The insulator glass will not shatter unless it is hit direct. Drive wedge or chisel into cut and the cap should split. The cement can the be tapped and broken away from glass because the mechanical key is no longer operative.  Cleaning: The cement should release cleanly, if not wire wool or Hydrochloric Acid will remove surface contamination.

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"The manufacturing and assembly of H.V. insulators ceased in 1970 when PB merged with Sediver (France). Pilkington still manufactures insulators at their Spring factory in the Transvaal South Africa."

It is interesting to note that in 1970 Pilkington Brothers merged with Sediver of France and since that time no longer manufacture high voltage insulators except at their Springs factory in the Transvaal, South Africa. We did, incidentally, by following their directions, succeed in removing the metal on two of the insulators. Some of you will scream at this -- maybe I will, too, one day. 

NOTE: Do not use this method on carnival glass insulators.

I have just recently borrowed a Pilkington catalogue from Mr. Woodward that he received from them in 1967. It explains what "toughened" glass is, why it is desirable, and how it is achieved. Permit me to quote directly from the catalogue:

"Insulator glasses are formed by pressing a measured quantity of molten glass into a steel or chilled cast iron mould. In large scale manufacture this process nowadays is carried out on an automatic machine and is continuous. The manufacturing cycle, being determined by the machine, can be closely controlled, which means uniformity of treatment for each glass shell in each part of the process. Toughening consists of first bringing the glass, after pressing, to a uniform temperature of about 700* C., and then rapidly cooling by means of a system of air jets. The rate of cooling is controlled to give the required distribution of surface compressive and internal tensile stresses. 

"After toughening, the glasses are visually inspected, and important dimensions checked for accuracy. Each glass shell is then subjected to two thermal tests to check that quality has been obtained, and to insure that the glass has been correctly toughened, since visual inspection does not indicate whether the insulator is toughened or annealed.

"Insulator glass shells and their appropriate metal fittings are cemented together in equipment designed to insure correct alignment of the components. The cement used is of a high early strength Portland type, and 'curing' is carried out under water at 20 degrees C. for at least 24 hours. 

"Armourlight insulators are proof against puncture by lightning surges and have a superior resistance to damage by power arcs. 

"In the event of an insulator shattering in service, due to a missile impact or arcing damage, the glass shed will fall away; but the insulator is so designed that, in this condition, it retains at least 80% of its specified minimum strength in the whole condition and will continue to support the conductor. 

"This feature is of considerable value in service, completely eliminating the need for live-line testing, since an insulator which is intact must be electrically and mechanically sound. A shattered insulator can, therefore, be located easily by visual inspection, either from the ground or from a suitable type of aircraft."

From the catalogue I learned that my insulator is a suspension disc, of the ball and socket type -- actually part of a large "string" insulator unit, each meant to be held to the next by means of a kink or cotter pin made of phosphor bronze. The metal cap is of heavily galvanized malleable cast iron. It is pictured below and offers a typical example of their complete line of suspension discs.

Following are sketches of the four pin type units manufactured by Pilkington Brothers, also bearing the trademark name ARMOURLight.

Pilkington insulators have been shipped all over the world for use on high voltage lines -- everywhere except the U.S.A.!!!