Carbon Filament with Opal Striped Bulb

During the 1890s The Edison-Swan United Electric Lamp Company excelled in the manufacture of so-called Fancy lamps, and offered a range of several dozen different types each having some feature of decorative value. Among the most intriguing both for their appearance as well as the skill required in their manufacture is the Opal Strriped model, which produces a highly attractive effect whether illuminated or not.

The base material for the bulb appears to be ordinary clear glass, onto whose surface a pattern of opal and opaque green glass has been fused. It is not certain whether this would have been applied after the bulb had been blown to its finished shape, or perhaps at an earlier stage where it might have been applied to a length of glass tubing, which was later blown into a bulb shape, producing the fancy patterns here as it inflated to take on the shape of its mould. It is suspected that the pattern was created by a printing method because it certain areas it is very finely detailed. Techniques exist by which coloured glazes can be applied in the form of a finely powdered frit, and then fused into the surface of the base material by heating.

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 insulation. The opal striping was a relatively expensive option - the 1893 Catalogue lists the opal striping as an optional extra costing 2s6d extra above the price of 3s9d for a standard bulb of this size.
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: Opal Striped Green 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, London Great Britain
Date of Manufacture: c.1890
Original / Present Value: 6s3d (1893) £28.49 (2011)
 
 
References: 1) Catalogue of the Edison & Swan United Electric Lamp Co. Ltd., 1893
2) Catalogue of the Edison & Swan United Electric Lamp Co. Ltd., 1896
3) Catalogue of Exhibits of the Ediswan Collection of Historic Lamps, c. 1930