'Enclosed' and 'flame' arc lamps
An online exhibition looking at the history, development and the engineers involved in the creation and manufacture of arc lamps. Find out how an arc lamp works and how electric lighting became a practical reality.
Enclosed and flame arc lamps were the final major developments in arc lamp design. In an enclosed lamp, the arc was contained in a small glass tube within the main globe of the lamp. This restricted the flow of air round the arc and reduced the consumption of the carbons by a factor of about five. Enclosed arc lamps therefore had reduced maintenance costs, but required more power. The enclosed arc was introduced by an engineer called Marks in 1893.
Flame arc lamps had cores of flame-producing salts added to the carbons. Mixtures of flourides of magnesium, strontium, barium and calcium were mainly used to make the cores. Adding a salt core increased the light output, and different types of salt core gave different colours of light. Salt cores were patented in 1889, but came into use slightly later than enclosed arc lamps.
Several companies manufactured enclosed and flame arc lamps - the enclosed arcs pictured were made by R.E. Crompton & Co. in 1914.
