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Author Topic: Dumet Wire Questions  (Read 4423 times)

Offline Tedd

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Dumet Wire Questions
« on: June 29, 2000, 09:12:00 pm »
Can anyone tell me, or refer me to another resource, when was "dumet" wire
invented, and when did it become widely used?

I have a Crookes (evacuated electrical discharge) tube which has wires
used to make glass-to-wire seals.

The wires:

- look coppery where they are not in contact with anything inside the tube
- look red/brown where sealed in glass
- in one case appear to be spot-welded to another piece of metal inside the tube

Does this description suggest "dumet" wire, or possibly some other?

I'm hoping to use info about this wire to help determine the age of the Crookes tube.

Thank you very much for any info,

Tedd

Offline Dave

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Dumet Wire Questions
« Reply #1 on: July 01, 2000, 11:17:00 pm »
I can't say that I am familar with Crookes tubes, but I can explain about the sealing of incandescent lamps and it could be similar to what you have. Dumet wire was first put into use around 1914, when it replaced platinum. A good type of metal is needed for the lead in wires through the stem press in order to mantain vaccum in the lamp. Right from the very early days of incandescent lighting, it was/is known that platinum "wets" the glass in the stem press, and this is a good sealant, so that the vaccum/gas won't leak out when the lamp cools and the wires contracts. Unfortunately platinum is an expensive material...so a reliable replacement had to be found. Several materials were used, but none proved to be good. Finally, it was found that conventional lead in wires coated with copper made a good sealant, and was cheaper to manfacture, and as I said, it was put into wide use in 1914 and is still in use today.
DMD

Offline Tim

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Dumet Wire Questions
« Reply #2 on: July 06, 2000, 05:33:00 pm »
Tedd,

I took a closer look at the tubes I have and found one with what looks like Dumet lead-in wires - see the picture below. Coincidentally (?) it's also the only tube I have that's a dud - it refuses to light depsite being in perfect physical condition  

Even though Dumet was developed around 1913-1914 I bet it wasn't used in Geissler tubes until several years later. Can anyone confirm this? I'm just guessing.......


 

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