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Old 28th Nov 2006, 11:26 pm   #1
DoctorWho
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Default GPO Blackened Brass on Candlestick Telephones

Does anyone know exactly what process the GPO used to use to blacken the brass on candlestick telephones? I've read that it was a chemical blackening, but what chemicals do you use?

I want to return a phone which has been polished to make the brass shiny back to the original blackened finish, but I have no idea how it was originally achieved or can be replicated.

Any advice appreciated.

Peter.
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Old 29th Nov 2006, 7:08 pm   #2
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Default Re: GPO Blackened Brass on Candlestick Telephones

Hi Peter,

Take a look at: http://www.chronos.ltd.uk/ and put blacking in the search engine.
If you ask for their catalogue, it has more information than is on the website. It may be of use.
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Old 29th Nov 2006, 7:58 pm   #3
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Default Re: GPO Blackened Brass on Candlestick Telephones

Peter,

the GPO phones were steel with a black enamel finish, at least the Tele. 156 is.

Some of the very early ones may have been brass, but I'm not sure. You may want to check yours against Bob Freshwaters site:

http://www.britishtelephones.com/telelist.htm

Jim.

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Old 29th Nov 2006, 8:39 pm   #4
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Default Re: GPO Blackened Brass on Candlestick Telephones

Thanks for the information, this is a picture of the telephone, it's a No. 2 Candlestick phone which, I believe, was originally chemically blackened and sadly someone has polished the brass up at some point in the past.

If anyone knows better then I'd certainly appreciate knowing, it I am right and it should be chemically blackened then I'd appreciate any suggestions on what to use.

Thanks again.

Peter.
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Old 29th Nov 2006, 8:44 pm   #5
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Default Re: GPO Blackened Brass on Candlestick Telephones

Right, I see what you mean now!

On my Tel. No 156, the earpiece has a thin layer of black Bakelite(?) over the brass case.

There are a number of blueing salts on the market, usually obtainable from clock suppliers, but I don't know if they work on brass - perhaps Mike Phelan can advise?

Jim.
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Old 29th Nov 2006, 9:35 pm   #6
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Default Re: GPO Blackened Brass on Candlestick Telephones

Thanks Jim, any advice appreciated.

Peter.
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Old 29th Nov 2006, 9:40 pm   #7
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Default Re: GPO Blackened Brass on Candlestick Telephones

Peter,

a bit of work with Google found this:

http://www.peterdyson.co.uk/acatalog..._PRODUCTS.html

there are several types opf brass colouring salt - you may have to try them on some scrap brass sheet.

This page may be useful as well:

http://www.mailleartisans.org/articl...y.cgi?key=3753

Jim.

Last edited by jim_beacon; 29th Nov 2006 at 9:49 pm. Reason: Added extra link
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Old 30th Nov 2006, 9:40 am   #8
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Default Re: GPO Blackened Brass on Candlestick Telephones

Quote:
Originally Posted by jim_beacon View Post
There are a number of blueing salts on the market, usually obtainable from clock suppliers, but I don't know if they work on brass - perhaps Mike Phelan can advise?

Jim.
Jim
Here I am.
"Blueing salts" is actually a bit of a misnomer. They don't actually blue anything.
Their purpose is just to melt at the temperature where steel oxidises to a blue, so, if you are blueing polished steel like screws or hands, you just put the items and salts in a crucible and heat it without having to monitor the rather critical temperature. It also serves to even out temperature variations.

Blackening brass or copper:
As you won't be able to get either antimony chloride or a mixture of ferric sulphate and arsenic now the best bet is Chronos, Mastergrave or any other model engineering supplier.
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Last edited by Mike Phelan; 30th Nov 2006 at 9:41 am. Reason: Typo
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Old 5th Dec 2006, 11:31 am   #9
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Default Re: GPO Blackened Brass on Candlestick Telephones

Jim & Mike, many thanks for the advice here, I had no idea that the original process used arsenic!! I'll look in to model engineering suppliers as you advise.

One point of interest I have found out since making this post, the telephone came from the Alexandra Palace railway station, and was rescued around the time that Dr Beeching closed down the line, so it will be nice to restore it back to the original appearance.

Thanks again for the precise information Mike, now I can work on getting the original look back.

Peter.
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