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Old 29th Nov 2019, 3:14 pm   #1
BRASSBITS
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Default Black oxide coating on brass

has anyone on here had any telephone brass parts coated/plated ?
how did they turn out, where did you have them done.
thanks
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Old 29th Nov 2019, 10:54 pm   #2
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Default Re: Black oxide coating

40 years ago, before I knew any better, I sanded down the case of my Bell No 1A and applied light oak polyurethane varnish, then polished the black gongs back to bare brass.

A little earlier than that I did the same to my late father's antique microscope, but the years are slowly growing the patina back.
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Old 30th Nov 2019, 2:12 am   #3
M0TGX Terry
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Default Re: Black oxide coating

I also have a 'brass blackening ' job awaiting resolution. It's the bezel around the dial aperture on an Osram Music Magnet. A horologist aquaintance kindly sent me a list of various chemical solutions for colouring brass and other metals, copied from a book in his possession. The book dates from well before the second world war. Sadly, the recipe for blackening brass begins with half a pound of white arsenic, which appears not to be available at any of my local chemists!
A horological supplier may be a source of something suitable? I've not pursued it yet as this particular job has slipped down my to-do list.
If anyone wants a copy of the relevant formulae (if the forum rules permit) I can post it tomorrow.
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Old 30th Nov 2019, 10:14 am   #4
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Default Re: Black oxide coating

Brine, chlorine bleach fumes and vinegar all discolour solid brass to varying degrees. Might be worth experimenting with with one or two small unloved pieces in the first instance.

Alan
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Old 30th Nov 2019, 11:11 am   #5
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Default Re: Black oxide coating

I have some Liberon black antiquing fluid (tourmaline) which is for aging brass, copper and bronze. I haven't used it for some time , as I remember the results can be a bit variable. After use the treated area is recommended to be covered in Jade oil to seal and protect from moisture. It also contains Selenium Dioxide and Nitric Acid so has to be used with care. Not sure if it is still available.
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Old 30th Nov 2019, 12:00 pm   #6
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Default Re: Black oxide coating

I had some candlestick telephone parts chemically blackened a couple of years ago at a local electroplating company. It was a bit experimental for them as they hadn't attempted before, I think they said the original oxidised finish involved cyanide and a process no longer allowed/used, but they achieved reasonable results. The finish had a very slight brown hue and was quite a matt sheen but looked better than bright brass for that application. There's bound to be some electroplaters to approach in Sheffield!
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Old 30th Nov 2019, 2:45 pm   #7
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Default Re: Black oxide coating

The 'salt and vinegar' process features extensively on YouTube and is a simple and cheap option to try:

https://www.youtube.com/watch?v=frqjEzfIDVE

And:

https://www.youtube.com/watch?v=wp8CK9_PA1w

J.C. Penny - who supply an extensive range of products used by cabinet makers and antique restorers - sell 'Antiquing Fluid', which is a cold patination treatment which will colour new or bright brass, copper, bronze ,mild steel or nickel to give an antique look. It is ideal for use in antique restoration. The finish can be sealed with Rustins Jade Oil, wax polishes or lacquers. The brass & copper fluid is available in two colour tones - black and brown. The website states that this product is an alternative for the discontinued Liberon Tourmaline & Haematite products.

There are four types of fluid:

Black : For all copper based alloys & mild steel.
Brown : For Copper & Brass, on Gilding Metal and Silver.
Nickel Black : For nickel based metals.
Fedox : Acid solution for imparting a red oxide rust on ferrous metals, such as mld steel, cast iron etc.

The fluids will generally have little or no effect on stainless steel, aluminium or chrome.

In use, it's diluted 1:10, and not outlandishly expensive - 250ml for 8.34 inc VAT + P&P:

http://www.jpennyltd.co.uk/shopping/...tion.php?id=50

The website give instructions for use.

Hope that's of interest.
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Old 2nd Dec 2019, 5:36 pm   #8
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Default Re: Black oxide coating on brass

Uncertain of material ( brass imitation ?), but I did have a decent outcome with the numbers on my door numbers .( Cheap & nasty due to being LA property ) . The finish suffered after some foreign sub ( to nth degree ) splattered the door etc with render and used some sort of acidic solution to remove the excess.
I used a fine wet & dry paper , then a wet & dry block ( wet of course ,with washing up liquid) , and finished off with a car scratch 2 grade kit. ( similar to Brasso/T cut. ). I then protected the surface with car spray lacquer .
As an aside, I've resurrected an old DVD using the 2 grade scratch kit ,removing the residue with meths.
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Old 2nd Dec 2019, 6:11 pm   #9
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Default Re: Black oxide coating on brass

Brassbits is wanting to get a black oxide coating though, not clean it off!
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Old 2nd Dec 2019, 6:31 pm   #10
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Default Re: Black oxide coating on brass

Local gunsmiths should be able to supply you with either 'gun blue' or 'gun black'.

I've used it for years on steel & brass. Works well for blacking in engraving work as well.

David.
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Old 3rd Dec 2019, 9:42 pm   #11
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Default Re: Black oxide coating on brass

Quote:
Originally Posted by Vintage Engr View Post
Local gunsmiths should be able to supply you with either 'gun blue' or 'gun black'.

I've used it for years on steel & brass. Works well for blacking in engraving work as well.

David.
I guess this is not the chemicals to add colour to carbon steel using heat to build up an oxide layer but a lacquer of some sort?
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Old 4th Dec 2019, 5:58 am   #12
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Default Re: Black oxide coating on brass

No, the blue or black surface coating on guns is produced by a chemical conversion process. I recall being in the USA many years ago and roaming through the sporting goods section of a Wallmart and they had had kits on sale for DIY bluing/blacking. I think they used a solution with cyanide in it, so they may have been withdrawn by now

In my experience, these processes are often something of a "Black art", and even if you have a written procedure from a reliable source, and you can acquire the chemicals, you'd be lucky to get a good result first time. There's usually a learning curve. People I know who are air rifle enthusiasts generally send them away to specialists for blacking when they do a rebuild.

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Old 4th Dec 2019, 11:10 am   #13
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Default Re: Black oxide coating on brass

I don't know what the original process was
but it was very durable with a shiny / gloss finish as on the gongs of wooden bell sets the tele 121 and various parts of the candlesticks.
the processes I have seen so for are not suitable for brass.
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Old 5th Dec 2019, 5:48 pm   #14
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Default Re: Black oxide coating on brass

The 1942 edition of "Machinery's Handbook" has a couple of pages on colo(u)ring brass in a variety of colours. There are several for black, but the only one that does not involve the use of Cyanide and/or Arsenic is as follows:

" Another cheap solution is composed of 8 ounces of sugar of lead, 8 ounces of hyposulphite of soda and 1 gallon of water. This must also be used hot and the work afterwards lacquered to prevent fading. When immersed, the brass first turns yellow, then blue and then black, the latter being a deposit of sulphide of lead".

Being an American book, the "gallon" would be the US gallon of about 128 fluid Oz, rather than the UK gallon of 160 Fl. Oz. No indication as to how hot is "hot". Lacquering is also recommended for all but one of the other processes

Last edited by emeritus; 5th Dec 2019 at 5:54 pm.
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Old 5th Dec 2019, 6:53 pm   #15
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Default Re: Black oxide coating on brass

Am I right in thinking that sugar of lead is lead acetate? Might not be easy to obtain these days. However, I imagine it can be made using lead (shot or fishing weights), vinegar and an oxidising agent like hydrogen peroxide. A resident chemist may be able to advise.

Alan
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Old 5th Dec 2019, 7:45 pm   #16
Dave Moll
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Default Re: Black oxide coating on brass

Certainly, Alan, Wikipedia agrees with you about sugar of lead being lead acetate (Pb(CH3COO)2). A quick look on eBay (no doubt other sources are available) does show lead acetate for sale, albeit not from the UK so the legality of importing it would need to be checked.
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Old 5th Dec 2019, 7:48 pm   #17
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Default Re: Black oxide coating on brass

Lead has been banned for fishing weights for a few years, but is still used for airgun pellets and roof flashing. When our roof was renewed a couple of years ago, I saved the flashing offcuts from the skip.
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Old 5th Dec 2019, 8:15 pm   #18
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Default Re: Black oxide coating on brass

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Originally Posted by emeritus View Post
Lead has been banned for fishing weights for a few years, but is still used for airgun pellets ....
Didn't know that as I'm not into fishing but I'm glad. Sounds like the game shooting lobby is more powerful than the fishing lobby.

Alan
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Old 6th Dec 2019, 10:54 am   #19
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Default Re: Black oxide coating on brass

Quote:
Originally Posted by Dave Moll View Post
Certainly, Alan, Wikipedia agrees with you about sugar of lead being lead acetate (Pb(CH3COO)2). A quick look on eBay (no doubt other sources are available) does show lead acetate for sale, albeit not from the UK so the legality of importing it would need to be checked.
This youtube video might be of interest - 'Making Sugar of Lead', which also outlines the history of it and how it got its name:

https://www.youtube.com/watch?v=lOjLuJyMmUQ
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