Insulator Collecting UK — Teleramics

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cordeaux Country

insulator cross section

Key distinguishing points

  • Internally threaded
  • 1 wire groove and ridge
  • older versions have a protruding inner shed
  • Predominately white / cream in colour
  • black composite and brown stoneware were also made
  • Designed in 1877
  • Used all over the country by the railways and GPO

The architypal standard pattern telegraph insulator has to be the the Standard Post Office pattern incorporating the internal J.H.cordeaux patent thread.

In 1878 a paper was read to the Society of Telegraph Engineers on 'Insulators for Aerial Telegraph Lines'. No fewer than 21 different styles had been tested. The all now familiar cordeaux pattern, with its rubber washer and screw thread won the day and in the UK was adopted as standard by the Post Office and the Railways. The London & North Western Railway, LNWR, started using cordeaux pattern insulators soon after these tests were completed. Some of the earliest dated insulators in the collection are stamped LNW.


Standard.... What standard? The so called standard pattern is found in many variants encompassing different sizes, materials, colours and even variations in shape from manufacturer to manufacturer.

Bullers Ltd, designated this size and style as their No.1. They are approximately 5" tall and 3" in diameter. Earlier versions can be identified by a longer inner shed, typically 1/4" protrusion. On later versions the inner shed is recessed by a similar amount.

Note the Railway company logo prominently stamped on the top front. GWR - Great Western Railway.


The larger brown ceramic version shown was stamped and supplied by Taylor, Tunnicliffe & Co. and is unusual in that it is just a tad oversized, compared to their normal No.1 variants, approximately 1/4" larger all round and almost chocolate in colour. A similar sized white version also exists within the collection.

The changeover from extended inner shed to extended outer shed appears to be about 1942 or 1943. No extended inner shed seems to exist after 1943 nor extended outer shed prior to 1942. Without further dated examples, I cannot be exact on the year nor 100% about the truth of the previous statement. Note. Only Bullers date their insulators.


A much smaller version of a No.1 is pictured here, Approx 3.5" high and 2.5" diameter, marked on top 'GPO' and made from a black composite believed to be 'Vulcanite' or possibly even 'Telenduron'.

Any information relating to this material would be gratefully appreciated.

Cross Sections

cross section of a pre 1943 standard Post Office pattern insulator

This broken example shows an excellent cross sectional view and its cordeaux thread can be clearly seen. This particular example is post 1943, a fact given away by the recessed inner shed. Note how deep the air gap between the outer and inner shed is and realise how much surface distance from the wire contact point, in the groove and the nearest earth point, the thread in to which the anchor pin is fixed is kept dry by design, thus reducing current leakage through moisture or dirt.

Also notice how far soot and smoke have penetrated up inside.

fat standard insulator

Thanks go to James Bancroft for furnishing me with this half standard pattern insulator he obtained from Scotland

As can be seen when comparing the 2 cross sections many differences can be seen. This larger variant is marked Jobson Brothers, Dudley, England. It was a cemented variant as can be seen from the two cement grooves. The top is much squatter and wider than a conventional standard yet they serve the same function probably with the same performance.

I estimate this variety to be from the late 1880's

A Purple Standard


This large Taylor Tunnicliffe & Co, (TTC), cordeaux pattern is one of two just acquired from the line side near Yeovil. It's a white porcelain body with a brown / purplish glaze. The top remains unglazed as if it were placed inside the kiln upside down.

Stamped into the top is a number 21, the significance of which is a mystery. I now have a large TTC, white, stamped 43 and a part of a Langdon marked 83. Any information on these markings would be gratefully appreciated.

Standard cordeaux Post Office pattern, Bullers Ltd.

Top row, left to right:- 1st - LMS, London Midland and Scottish Railway, printed. 2nd Stamped Bullers limited London, complete with wire binding. 3rd GWR, Great Western Railway, printed.


Bottom row, Black Vulcanite / Telenduron, embossed T5 on top. Red power transmission cordeaux, stamped with Bullers hand symbol and illegible date, 19?0. Brown stoneware, stamped GPO on top.

A Brown Buller Jobson


One of my favorite examples of a standard Post Office pattern insulator is this very early, non threaded variant in brown.(Strictly speaking, not a cordeaux pattern!)

Impressed on its top sloping face, Buller, Jobson & Co.Ltd Dudley, England, it dates from between 1885 and 1888.

I rescued it from alongside the London South Western (LSWR) main line to Exeter where it was still attached to a replacement Concrete telegraph pole which was being used as a support in a river bank. Sadly it was positioned upside down and frozen water has caused it to split clean in half.

This breaking in half allowed me to seperate it from its spindle and retrieve for my collection.

A lost Irish Insulator?


This insulator was found in a drainage ditch where the Great Western line from Oxford to Wolverhampton crosses the Midland line to Birmingham from Gloucester near Worcester and as such its location is unable to give us its company of use.

Made by Bullers in 1938, other than the Bullers logo the only marking is P & T on the top front face and in view of other information I believe this means Post and Telegraph, of Irish origin!

It has an extended inner shed, the photograph just does not give it justice and other than a few stress cracks in the base of the inner shed it is in perfect condition.

A White Buller Jobson TP287

cordeaux insulator

This insulator, at first glance, appears to be an early standard Post Office pattern but the inscription tells us it was made between 1885 and 1888 by Buller, Jobson & Co Ltd, Dudley England, thus making this a very early model indeed.

The top front sloping face is impressed T P 287, possibly a reference to its ability to be used as a power or telegraphic insulator and a pattern number of 287. The reverse face is stamped PATENT

Bullers designs were running around T185 and T190 by 1881 so T287 would certainly be acceptable for 1885 to 1888.

Two similar broken examples exist within the collection both stamped Jobson Brothers, Dudley England, 1876 to 1874, and again on the top sloping face with the word PATENT, but this time, there is no T No. backing up the theory that this was a Bullers numbering scheme not a Jobson Brothers scheme.

Update December 2005

Thanks go to Tris Horton for providing me with an intact example.

Latest find

A trip to Melton Junction, Melton Mowbray in November provided useful insulator data if not many insulators

tubular spar

Between the junction and the GNR embankment small Cordeau fragments were found still attached to their spars. What made this find unusual was the spars themselves. Made from tubular steel in a modular construction, each main centre piece was approximately 2 inches in diameter with a central pole fixing hole and a spindle fixing hole at either end. Each end had a smaller diameter extension fitted internally and held in position by the insulator spindle on the main section. These outer extensions were also made with a spindle hole giving the complete spar a total of 4 spindle holes.

Although none of the insulators were complete all were dated LMS 27 on the top sloping face and illegibly stamped with a letter code on the top. I therefore conclude the spars are themselves at least from 1927 but possibly earlier.

A Red GPO ??

red insulator

An unusual red standard Cordeaux variant has come to light recently. This is dimensionally the same as any normal Cordeau and is dated 1942 with the Bullers logo on it's top and stamped GPO with the arrow logo above it on the side. It is unusual in that it is red and the first I know off.

This GPO variant seems out of place as it was found within a run of red Cordeau's made by Bullers all dated and stamped LMS. Could this have been a factory mix up i.e. it happened to become mixed amongst the LMS stamped insulators due for spraying, got sprayed red and sent out to the LMS for installation.

I expect the telegraph engineer had climbed up the pole to install some insulators, found this one marked incorrectly but rather than climb down again swap the insulator and climb up again fitted it anyway

The question remains: Did the GPO use or ever specify red insulators? If anyone knows, why not let me know.

Latest Donation

Thanks go to Jim Gough for providing me with lovely purple red Wade in exchange for a few of my surplus insulators

Red Wade Insulator

I have yet to give this a good clean or take a proper photo, so if the image appears strange, it's because it is.

Unlike Bullers red insulators the Wade red is nearer a burgundy. The interior is glazed in the usual clear, leaving it bright white in appearance. The red however, appears to be an overglaze as if it was a normal white version refired with the coloured glaze. Certain areas appear to show rubbing and some spotting is present where the red glaze has not entirely covered the white glaze.

Below the Wade hand appears the letter M and as in the Wade page this remains a mystery.