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Carbon Filament with Coloured Glass Bulb |
Whereas today the various lamp manufacturers have rationalised their ranges and offer just five or six plain colours, it is astonishing to glance at the Ediswan catalogues of the 1890s and appreciate the rich variety of colours that were offered. All versions employ natural coloured glass because it would be another two decades before coating materials were developed that could withstand the high operating temperature of the carbon filament lamp without fading or burning off. A staggering fourteen different glass colours were offered plus a further selection of coloured opal versions, and as if that was not enough to satisfy the Victorian consumer, a footnote indicates that the company would be happy to entertain requests for additional hues not listed. This lamp bears a paper label numbered 740, which identifies its colour as Azure Blue. It is thought to have originated from a salesman's set of demonstration lamps.
The rest of the construction of this lamp is similar to ordinary types of its era, having platinum lead wires pinched directly into the neck of the bulb. The filament is secured with a deposited joint of carbon. The bayonet cap is made from standard pipefitters' 7/8" (22mm) brass tubing with plaster of paris insulator. Different glass colours commanded different prices depending on their composition, this model costing just 1 shilling above the price of the clear version.
| Manufacturer: | The Edison-Swan United Electric Light Co. Ltd. | |
| Lamp Power: | Approx 60 Watts | |
| Lamp Voltage: | 100 Volts | |
| Lamp Current: | 0.6 Amperes | |
| Cap Type: | B22d | Brass + Plaster of Paris |
| Bulb Type: | P-57t | P-18t in eighths/inch |
| Bulb Finish: | Clear Azure | Soda-lime glass |
| Filament Type: | Squirted Carbon | |
| Atmosphere: | Vacuum | |
| Luminous Flux: | ||
| Luminous Efficacy: | ||
| Beam Intensity: | N/A | |
| Beam Distribution: | N/A | |
| Colour Temperature & CRI: | CCT: | CRI: |
| Chromaticity Co-ordinates: | CCx: | CCy: |
| Rated Lifetime: | Approx. 800h | |
| Burning Position: | Universal | |
| Overall Length: | 100 mm | 4 inches |
| Light Centre Length: | ||
| Factory: | Ponders End | England |
| Date of Manufacture: | c.1890 | |
| Original / Present Value: | 4s9d (1893) | £21.66 (2011) |