BulbCollector Forums
BULB DISCUSSION BOARDS => Antique Bulb Discussion => Topic started by: armothecanus on November 17, 2008, 09:42:33 pm
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I am looking for anyone that can tell me what particular type of glass this bulb is made of, the type of adhesive that was used to attach it to the base and what was used to attach the filament to the posts.. The stamp on the base says that it is from 1904.. I would be greatful for any help.. Preston
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The bulb is made from fairly ordinary soda-lime silicate glass, however with small cerium oxide dopant to improve the moulding characteristic on the automated production machinery.
The basing cement is made from a 2-component mixture. The bulk of the material is composed of marble dust, mixed with lithopone (hardener), and tung oil which assists flow and prevents sticking in the automatic machines which were used to fill the bases with cement. This mixture is then added to the binder solution which sets the viscosity to the required degree. The binder is mainly comprised of industrial alcohol as a solvent, together with silicone resin, colophony, shellac and hexamine. Sometimes malachite green is also included as a temperature indicator dye. The result is a thick paste like cement which is thermally cured at around 210 celsius for a few minutes, and the resulting reaction achieves a strong surface bond to the glass bulb. There is no real bond to the metal base which is held in place primarily by friction, owing to the fact that the cement expands during cooling.
The filament is attached to the lead-in wires simply by a mechanical clamping operation.
The 1904 date on the base refers to the patent of its design, the lamp itself is probably somewhat later.