Australian Insulator History.

Thanks to Marilyn Albers and Mr. N.R. Woodward of Houston who are the authors of the book "Glass Insulators from Outside North America". The text on Australian Insulators shown below is from their book with their kind permission.
Books can be purchased from

History on Australian Insulators .

Prior to 1925, Australia relied solely on insulators imported from other countries. Most of these came from New Zealand, England, France and the United States.

Australian Glass Manufacturers was established in 1915 as a conglomerate, which included the Melbourne Glass Bottle Works (1872-1915) and Vance & Ross of Sydney (1904-1915). In 1926, this company became the first to manufacture glass insulators in Australia. Their factory was, and still is, located on South Dowling Street, South Sydney. During the 1926-1942 period, many fruit jars, insulators, pie dishes and other glass items were manufactured with the trade name AGEE pronounced A.G. for Australian Glass. With the exception of insulators, many of the above items were made of borosilicate glass, a toughened type of glass similar to Pyrex. Borax was not available in Australia, and while the higher selling price of certain products, such as heat-resistant cookware, probably justified the cost of importing this mineral, it was simply too expensive for the
manufacture of insulators.

During these years, the company produced seven styles of glass telephone insulators including CD's 121, 154, 420, 421, 421.1, 422 and 490 (Type I, II, and III). With the exception of the very early runs of CD 121, which are not marked at all, all seven of these styles are embossed AGEE.

The Sydney plant began production of CD 121 tolls in about 1926. Most of these insulators are made in aqua, charcoal grey, or various shades of greens and purples.
According to one reliable source, the purple colours are the result of either the glass formula or the minerals in the cullet used for a particular batch of insulators. A few rare examples of unembossed 121's have been found in clear, dark amber and emerald green. CD 490 Type I bells were also introduced at this time. Glass colours are medium to royal purple, pure grey, and two-tone light amethyst with green. We refer to these earliest AGEE bells as Type I because of their narrow, straight sided domes, rounded wire groove rims and nearly flush inner skirts. A rare variety exists with four sharp drip points rather than a completely smooth base. Although the wire groove rims on both styles were less than perfect for holding the wire down, these were the major Sub (CD 121) and Trunk (CD 490) insulators in use during the mid to late 1920's.

Sometime between 1929 and 1930, Australian Glass Manufacturers received a special Order for CD 154's from the South Australian government. As far as we know, most of these were produced during that time period and were used only in that state. These insulators have mould numbers and round drip points. Glass colours are sage green, grey or medium to dark purple. With its American threaded pin hole, the AGEE 154 is a copy of our familiar Hemingray 42 insulator, which was being used in South Australia at that time. While both units could be, and probably were used side by side on the same line, the AGEE 154 was designed to replace its American twin.

CD's 420, 421 and 421.1 made their appearance in the mid to late 1920's as well. Glass colours are limited to aqua for 420 and amethyst for 421 and 421.1. We believe that these three styles were the result of sequential experimentation, which eventually led to the development of CD 422 as the Sub (Subscriber) insulator of the 1930 to 1942 period.
None of the 420's, 421's, 421.1's or Type I 490's have mould numbers, which leads us to believe that these were all made prior to 1930, since mould numbers on AGEE insulators were well established by 1930. All of the AGEE: 422's have mould numbers, and while most are dated, many are not. They were produced in a rainbow of colours, including greens, grays, blue grays, and several shades of purple, from light to dark until 1937, when straw colored 422's were introduced for the first time. The only dates we have seen on these later specimens are (19)37 and (19)38, but it is likely that production of this particular style continued until 1942, when Crown Crystal Glass Company Ltd. assumed responsibility for the manufacture of glass insulators.

CD 490 Type I AGEE bells began having problems almost from the beginning of production. Because the glass was thin from the wire groove up, the insulators were subject to fractures in the neck area. And, as stated above, the shallow wire groove rims were nearly useless. So, somewhere between 1928 and 1930, Australian Glass Manufacturers introduced an improved version which we refer to as Type II. The dome remained straight and narrow (and fragile), but the inner skirt was raised a bit and the wire groove rim was sharp and angular. Glass colours range from light to medium to rich deep amethyst. Mould numbers are embossed on all of these Type II bells.

But there was still room for improvement, so Type III 490's were introduced in 1930 as the glass Trunk insulator of the 1930 to 1942 period. While maintaining the raised inner skirt of the Type II bells, this new style proved to be more structurally sound with its wide angular dome and thick angular wire groove rim. All of the Type III bells have mould numbers and dates of (19)30, (19)37 or(19)38. Those units carrying the 30 date were all medium to dark purple. This 30 did not necessarily mean the insulator was manufactured in 1930, but rather from 1930 to 1937. Type III 490's of straw colored glass were produced for the first time in 1937. Specimens are dated either (19)37 or (19)38. These insulators, however, saw limited production because of some fairly stiff competition from a local pottery. In the mid to late 1930's, a company known as Robert Fowler Ltd. of Sydney had begun turning out thousands of the large porcelain bells (U-1502) and as a result, demand for the AGEE glass equivalent dropped considerably.

While the U-1502's seem to have been preferred to AGEE Type III glass bells for use on
lines, they were far from perfect. By their very design, the flared out skirts allowed dirt to accumulate easily. In wet weather, this increased the surface leakage between wire and pin. The resulting low insulation resistance created a lot of static on the lines. Something had to be done, so in 1936 a decision was made to redesign the insulator.

By March, 1938, four types of insulators (three porcelain and one glass) were chosen for testing purposes on certain trunk lines between Melbourne and Dromana in the State of Victoria. These styles included U-1502, U-1542, U-1154 and CD 432. U-1502, of course, was currently the standard porcelain Trunk Insulator of Australia, U-1542 was the standard B.P.O. (British Post Office) Trunk Insulator, U-1154 was the "new" design combining the best features of the first two, and CD 432 was included as a modified glass version of U-1154 in order to examine the value of this material for the particular purpose. Australian Glass Manufacturers agreed to produce a sufficient number of the 432's to equip the lines being tested. These unembossed units were all made of the same greenish grey glass.

Some insulators designs: U-1502 uses 1 9/32" thread, U-1542 uses a 5/8" thread and the U-1154 & CD-432 uses 1" thread.

After examining four months of test results, belief in the single skirt design of U-1154 was confirmed. It became the new porcelain Departmental (P.O.) Standard, known as "Insulator, Trunk, L.S." (Long Skirt), which distinguished it from the previously accepted Trunk Insulator.

The CD 432's proved to be inferior for the test. Many were found to have cracks in the glass, even during installation, and a great number actually broke while in service. Obviously, further testing was needed. To our knowledge, only three specimens of this insulator remain in existence today.

In 1942, Crown Crystal Glass Company Ltd. (C.C.G.), another Sydney glass manufacturer, merged with Australian Glass Manufacturers. C.C.G. took over glass insulator production at this time and, in some cases, previously used moulds as well. Though their catalogue offered many other glass items, such as AGEE Pyrexware, bowls, vases, lamp bases, huricane lanterns, fly traps, inks and other sundries, all insulators produced during this 1942-1950 period are attributed to the C.C.G. plant in Sydney. Several smaller glass factories joined this amalgamation during the 1940's and the resulting parent firm was known as Australian Consolidated Industries (A.C.I.).
However, certain items, including insulators, continued to be produced under the old tradename,

The three telephone styles manufactured at the Crown Crystal Glass plant in Sydney included CD's 422, 423 and 430. All of these insulators are embossed with the company initials C.C.G., followed by mould numbers and dates. Some are dated directly, i.e. (19)42, 43, 49, 50, etc., but most of these units have coded dates with double dots (:) to represent the years. For example, 4 is for 1945, and strangely enough, 4 indicates 1950. By extending the rows of dots, moulds could be up-dated without having to make new ones. CD 422's saw very limited production. The only dates appearing on these insulators are (19)42 and (19)43, likely indicating the first and the last year this
style was produced by C.C.G. Glass colours are limited to light straw and smoky clear.

In 1942, CD 423 was introduced as the new Subscriber insulator. Because it was so well accepted, it was produced in great numbers. This style proved to be the most common and widely used of all Australian glass insulators. Embossed specimens exist in clear, very light peach, light green, medium to dark amber, and pale amethyst. Specimens in amethyst are extremely rare, with only a small number having been found in the western part of Victoria.

Perhaps Australian Glass Manufacturers were still smarting from the enthusiastic acceptance of U-1154 as the new porcelain Trunk insulator of 1938, and remembered only too well that its own glass equivalent, CD 432, had fallen far behind in test results. This ever present threat of competition must have kept designers busy with further testing at the Sydney plant., because in 1942, when Crown Crystal Glass took over insulator production , they proudly presented their answer in glass. CD 430 was dubbed the new Trunk insulator. Like its forerunner, CD 432, it was tall and narrow and maintained the same single skirt design, but it had only one wire groove instead of two. Overall, it was a sturdier insulator and it was a success! C.C.G. 430's exist is a wide range of beautiful colours including clear, straw, smoke, light green, peach, chartreuse, medium to dark amber and several shades of amethyst.

In 1951, Australian Glass Manufacturers moved insulator production to their plant in Hobart, Tasmania, where three styles were manufactured with the A.G.M. embossing, including CD's 423, 430, and 590. Here again, all units have mould numbers and dates. While a few are dated directly, i.e. (19) 59, 61, 62, etc., most carry the familiar coded dates with numbers and dots.

CD 423's were produced in straw, light greens and several shades of medium to dark amber. A handful of specimens are known to exist in bright yellow. A few in straw were dated in West Australia with the letters SUB embossed on the back side of the skirt below the coded date 58::

On some A.G.M. 423's, one can see the imprint of an unknown trademark at the top of the
hole inside the glass. It can best be described as a circle enclosing the letter L and an "arrow". We believe these figures were engraved on the end of the threaded plunger by some specialty steel firm.

A.G.M. 430's were not nearly as colourful as those made by C.C.G. Specimens exist only in light greens, peach and straw. The latest date observed on one of these insulators is 61: for1962. On one example, the Roman numerals VVI were used to indicate the date of manufacture. Regardless of the mould maker's intentions, this combination of numerals is incorrect, and does not indicate any particular number.

In 1951, A.G.M. introduced CD 590, a low voltage cable-top insulator known as "Pin Type PI-3". This style was made in very limited quantities and only during that one year.
The first ones were of dark amber glass, and those that followed were produced in straw and shades of light green. While all CD 590's are scarce, those in straw and amber are considered to be even more so. Because this insulator was unsuccessful, it was discontinued.

In the early 1960's, the change from overhead lines to underground cables lessened the need for insulators, thus creating a surplus. As a result, the A.G.M. plant in Tasmania ceased insulator production in 1962.

The following is a direct quote from Bernard L. Warren, a leading authority on Australian
glass insulators: "Australian Glass Manufacturers, and later Crown Crystal Glass, had absolutely no competition for their glass insulator production and, because there were no private telephone or power companies in Australia, they sold only to the Government Entities. Australian TELECOM was it. Being a branch of the Post Office Department under the Postmaster General, it was 100% government owned. The seven State Electricity Commissions (SEC) controlled all power production and distribution. Two or more states would sometimes cooperate in giant projects, such as the Snowy Mountains Hydro-Electric Project.

All this resulted in single government buyers, and reinforces my theory that only the best AGEE, C.C.G. and A.G.M. Subscriber and Trunk insulators were produced and marketed at any one time. If TELECOM, or in some cases, the State Railroad Agency, didn't like the current Subscriber and Trunk insulators of glass, they could go to the Australian porcelain insulator manufacturers or to foreign suppliers".

Generally speaking, porcelain insulators came to be preferred in Australia, because glass had a higher percentage of breakage and lower insulation, especially under wet conditions. Glass was also more costly to produce. But in time, it proved to be even less expensive to import porcelain insulators than to manufacture them locally. Consequently, one can find specimens in Australia that were made in New Zealand, Japan, China, France, Czechoslovakia, England and India.

France, however, did supply Australia with glass insulators for both high and low voltage use. One can see units embossed EIV, L'ELECTRO VERRE, and ISOREX still in use on working lines. Examples are CD's 378, 378.6, 378.8, 390, 530, 560, 6Ol.l, 1065, 1067.1, glass suspension insulators, etc.

CD 494 is one French made telegraph style which deserves special mention because examples are extremely rare. Units are embossed ISOREX 1030. The colour of glass is dark green. This insulator is nearly identical to its porcelain counterpart, U-1502, and since the 494 has been found only in New South Wales and Victoria, the two styles were likely used side by side on Trunk lines in those states. The small number of CD 494's still in existence suggests that TELECOM, in one of its efforts to find the perfect Trunk insulator, may have turned to France and requested a special order of this style in glass.

CD's 343.2 and 344.2 are probably British imports. These insulators are not embossed but, with their copper-clad crowns, they very closely resemble units made by Pilkington Brothers in St. Helens, a firm which merged with SEDIVER of France in 1971. (See ENGLAND)

The authors owe a debt of gratitude to Bemard L "Bemie" Warren, of Anchorage, Alaska, for supplying much of this information on Australian insulators. In recent years, Bernie has made several extended trips "Down Under", and spent hours walking the lines, collecting and studying insulator specimens and talking with people knowledgeable about the telecommunication system and the manufacture of glass insulators in Australia. His research efforts were greatly aided by one collector in particular, Laura Monckton of Sydney.

The story behind CD 432 and its use as a test insulator on Trunk lines between Melbourne and Dromana was taken from R.M. Osborne's article "The New Trunk insulator", which appeared in a 1939 issue of The Telecommunication Journal of Australia.

Manufacturers and date markings as moulded into insulators