Salt water dimmers, which are an example of liquid rheostats, were used in theatres after the introduction of electric lighting to control the brightness of the lights on stage.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/b/bf/Salt_water_dimmers_at_Alexandra_Palace_Theatre.jpg/220px-Salt_water_dimmers_at_Alexandra_Palace_Theatre.jpg)
Electric Lighting
editElectric lighting replaced gas in theatres from the 1880s. The first theatre to replace the gas lighting totally with electric lighting was the Savoy Theatre in 1881.[1]
Salt water dimmers
editA dimmer consisted of a glass jar filled with salt water with a metal electrode at each end. As the upper electrode was moved away from the lower[2] electrode, the resistance increased and the lights got dimmer.[3][4][5] The brightness also depended on the concentration of salt in the water.[3] The switchboard built at Her Majesty' Theatre, London in 1897 had a dimmer scale of 0 to 10, whereas gas lighting only had 3 levels.[1]
The salt water need to be refilled regularly, the metal electrodes corroded, and the dimmers emitted a strong smell.[3][5] The dimmers were hazardous both because of the flammable gases produced and the potential for electric shocks.[3][5]
Salt water dimmers were gradually replaced by semiconductor dimmers, the last dimmers in London theatres being replaced in 1959.[6]
An example of a saltwater dimmer can be seen backstage at Alexandra Palace Theatre in north London.[citation needed]
References
edit- ^ a b Booth, Michael R (1991). Theatre in the Victorian Age. Cambridge University Press. p. 90. ISBN 052134837-4.
- ^ "Counterweight systems". Theatre Crafts.
- ^ a b c d Bastow, Jonathan (2020). "Salt Water Dimmers". YouTube.
- ^ Lounsbury, Warren C. (1967). Theatre Backstage from A to Z. University of Washington Press. ISBN 978-0295740911.
- ^ a b c Yadav, Deepakkumar (2020). "Salt Water Dimmer, Resistance Type Dimmer, Light Dimmer". Deepakkumar Yadav.
- ^ "Liquid Dimmers". Theatrecrafts.