Collection of nine prototype low pressure mercury ultraviolet lamps with complex seals
Entry/Object ID
2026.42.1
Description
Collection of nine prototype low pressure mercury ultraviolet lamps with complex seals
Use
The significance of these lamps is great because they were all experimental low pressure mercury lamps at a time when the metallic alloys used to hermetically seal quartz or fused silica were not developed yet. They have a variety of seals, including graded, cast, and combinations of the two.
Context
Graded seals are when two different very melting temperature and coefficient of expansion glasses are joined by a series of more similar melting and coefficient of expansion glasses which vary slightly so that one can be joined to the next without cracking upon cooling. In the case of these quartz or fused silica lamps, the intermediate glasses had to be developed first. The first lamp, the most complex, uses a soft uranium oxide glass with as many as a dozen intermediate glasses all within the last inch of where the electrodes enter the glass. Other lamps use a fine capillary wire (typically tungsten) melted in a heavy wall glass where leakage would be minimal...this finally is backed with a metal cap that is cast with the low-melting element indium, which slowly expands upon cooling. This extremely rare collection was found by Frank Jones and is on loan to the museum and contained in a special display case to prevent breakage.
Collection
Turn Of The Century Electrotherapy Museum
Acquisition
Accession
2026.42
Source or Donor
Jeff Behary's personal collection, gift from Frank Jones.
