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Old 17th Feb 2012, 2:22 am   #83
Join Date: Jan 2012
Location: Brentwood, Essex, UK.
Posts: 3,050
Default Re: Another unusual plug and some other questions

In 1893 the lamps were still hand made and used platinum for the lead-in wires, DUMET not having been invented then.

The complexity in manufacture is apparent from the following item from the Model Engineer for 1904.

In the evening of Monday November 7th. a party of twenty-six members paid a visit to Messrs. Robertson’s Incandescent Electric Lamp Works at Hammersmith. The party were met by Mr. Robertson and conducted in two groups over the whole of the very extensive factory, every detail of the production of Robertson electric lamps being shown and explained, the members thus having an opportunity of watching the growth of a complete lamp through the thirty-seven different stages, including the manufacture of the raw filament, drying, carbonising, fitting the platinum entering wires, flashing, sealing in bulbs, exhausting capping, grading the candle-power by photometer, testing and packing, &c. The extreme care taken to ensure efficiency in every stage of manufacture and the multiplicity of tests applied much impressed the party, and at the close of what was considered to be one of the most interesting and instructive visits made during the past year, the hearty thanks of the party, was tendered to Messrs. Robertson and Wilson and their assistants for the way in which they had arranged for the entertainment of the visitors.

[The Model Engineer and Electrician, December 1, 1904 page 506]

In 1904 Henry Loring of the Robertson lamp works wrote a book entitled "From the beginning", profusely illustrated with photos, that explained all of the 37 stages referred to. I had read, and made an indifferent photocopy of, the volume that used to be in the GEC archives, but the IET library has a copy. "Flashing " involved the female operative immersing the filament in liquid benzene and energising it so that it glowed under the liquid, causing disassociation of the Benzene so as to deposit carbon on any hot spots, thereby making the filament more uniform.

Nasty stuff, Benzene. In the 1970's we were testing our PLL receiver boards immersed in Benzine as it has about the same dielectric constant as the Araldite that we were using to encapsulate the finished product [someone had borrowed a gallon of the stuff from the chemistry lab downstairs]. I mentioned this over a game of cards to one of my friends who was an industrial chemist and he nearly fell off his chair. After he sent me the safety sheet [progressive irreversible brain damage from inhaling fumes: known carcenogen; nothing greater than 250ml to be used outside a fume cupboard] the Benzene went back to the chemistry lab forthwith!
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