In search of the salt water dimmer
From A History of Light and Lighting:
SALTWATER DIMMER – (a 1900)
Soon after the development of the electric filament lamp, applications were immediately found in the theatre for this exciting new invention. New lighting fixtures and methods of control were quickly developed and put into use. One early means of lamp ‘dimming’ was through the use of the salt water dimmer. The dimmer consisted of a tank (or barrel) of salt water brine with a permanent electrode submerged. As a second electrode was slowly raised (or lowered) into the brine, the conductivity between the two electrodes would increase (or decrease) respectively. Lamps connected in series to the dimmer, would be dimmed accordingly. It was not uncommon for a theatre to have a large number of these dimmers and it is said that the heat from the boiling brine would often help to heat the backstage areas. Undoubtedly messy and difficult to operate and maintain, the electric salt water dimmer was soon to be replaced by the somewhat more efficient (and dryer) electrical resistance dimmer.
As a lighting guy, I am very much into the history of theatre lighting. One thing I still want to see is a actual salt water dimmer that was (or god-forbid, is) in use at at theatre. Where are the photos of these former mainstays of the early days of electrical stage lighting? Does anyone still have one, or more? This is the only thing I have found so far, and it is just a trinket for the rich.
Hudson & Gaines
Have a look at this handout from a theatre class.
http://www2.sunysuffolk.edu/kankelj/TH16/handouts/salt_water_dimmer.htm
Looks pretty scary.
Enjoy
Very cool. That is better than I have found before. Thanks!
Still looking for a photo of one…
I can remember some gigantic old rheostat systems but I don’t think I actually ever saw a old salt water system.
If Bill Williams doesn’t have a picture of a salt water dimmer then who does? If you do find an image, let me know over at On Stage Lighting. Most of our readers have probably never even heard of them.
Best wishes
Rob
PS Patrick, nice to see that you used the much missed Hog II at your wedding. I personally banned all stage lighting and related techie stuff from my wedding day. Although the best man was a lampie who could be relied on in any situation – touring or wedding.
You know, we should just build one at work. I’m sure Bob could provide some insight, or at least just shake his head…
A friend of mine in undergrad tried to build one as an independent study. He worked on it for a while, but never got the brine mixture right: Too much salt and there wasn’t enough resistance and the lamp never dimmed regardless of how far apart the contact points were. Too little, and the two contact points had to be RIGHT next to each other to get even a small glow. It is apparently a very narrow range of salinities that provide the right conductivity. He eventually got it to work — more or less — but never found exactly the right salinity to make it work really smoothly.
I suppose you could start with pure water with the controls at the 50% position and add salt with the power on until you got roughly 50% brightness, and then check for range of control. I’m betting that would get you fairly close to the right salinity as a first approximation, or at least closer than other methods …
I work for Lutron Lighting controls. In my search for an image of a saltwater dimmer I found this link: : http://www.theatrestrust.org.uk/resources/images/show/7075-salt-water-dimmer-at-the-alexandra-palace-theatre
Hope it helps!
While i’ve not actually seen a photo of one i have come across many illustrations of them. You might also want to search for piss pot dimmers see the Wiki for ‘Dimmers’
In the 1960’s I was the lighting person for an amateur theatre group in small town NZ. I built a number of salt watewr dimmers using 4ft long x 6″ diametre glazed drain pipes. I placed a bronze coated circular slab of steel inside the bell end of the pipe and cemeted it into place with good quality mortar. A heavy insulated lead was soldered to the plate. After the cement had matured I would upend the pipe and it would stand nicely on the bell end. Filled it with water and suspended a 5.1/2″diameter billet of steel on a nylon rope and had an insulated flex soldered to this plate. Filled the pipe with pure water and with the “weight” suspended at 50% added salt until I got roughly a half power dim on the lighting load. I made a series of these pipes for different ciiurcuits. It took a bit of balalncing of the brine so that everey circuit had the same dim ratio as the “elevctrodes”were moved up and down. I then made a master dimmer using a 24″ drain pipe this was put in fron of all the other dimmers, and also was wired through a different circuit to the house lights.
The only problem was the brine would come to the boil during a lengthy
dim. I had all these pipes installed under the stage in a loncked cabinet and the ropes passed up through the tsge floor and up to a lighting control platform in the fly.
I could get really smooth dims – both fast and slow by pulling on the ropes which had a counter weight system.
One had to wear gum boots (Wellingtons) and rubber gloves when topping uo the pipes while live.
Our village electrician nearly had a fit when he saw what I had wired into the local town hall electrical system. The first show we did with all this stuff in place, the audience were enthralled when for the first time in it’s 60 year life – the town hall house lights dimmed as the show opened.
Sorry I don’t have any photo’s. I don’t think I wanted any evidence.