Darkening steel screw heads

[districtgrandmaste]

I've been asked to provide some 7BA screws to repair a nineteenth century equine statue.

I spoke to the Horology people and they suggested leaving the screws overnight in a cup of tea - the tannins should turn the steel black they said.

Well the tea wasn't much after twenty four hours but the screws had darkened. However a wipe and they were shiny again!

Anybody got any better method?

[gwrfan]

Hi,

Member Alan Stepney has some helpful hints here:

www.alanstepney.info/page36.html

Geoff

[ron]

Bit drastic, heat the screws to red heat and quench in used engine oil.[mineral]
Ron

[the_viffer]

gwrfan said:

Hi,

Member Alan Stepney has some helpful hints here:

www.alanstepney.info/page36.html

Geoff

I'm not certain many of the ingredients are available any more.

I don't recall seeing sodium hyposulphite (ie sodium thiosulphate) on sale for years. Maybe the more old fashioned photographic suppliers have it.

Lead acetate (sugar of lead: it really does taste sweet) is too useful as a poison to be easily available.

Caustic soda drain cleaner is easily available.

Iron chloride you can get from Maplin.

Gallic acid make your own from oak galls if you are desperate but otherwise I'm not aware of retail supplies of it.

Antimony chloride is also too toxic to be commonly available.

Copper sulphate is cheapest from farmers' suppliers.

Ammonium sulphide is sufficiently toxic that I would not handle it outside a properly equipped lab fume hood.

Sweet spirits of nitre is as of course you'd guess ether. You could probably get from model aeroplane people.

I think Ron's idea is better. Or what about Jenolite or similar rust treatments that turn steel dark?

[GWRdriver]

Quenching in engine oil has been the technique I've used for years. Cheap and effective. You needn't heat to full red and the older and grungier (carbon-laden) the engine oil the better, or should I say the blacker.

[ron]

The way the world is nowadays if you go to the chemist looking for some of these chemicals you'll end up one of these people who gets arrested amid great publicity by the anti-terror squad and then gets quietly released a couple of weeks later. ;D

Ron

[the_viffer]

Ron

It is remarkable what materials are still available if you know where to look especially with a bit of lateral thinking. It is also remarkable what disinformation is available about some of these materials on the web. Here is probably not the place to discuss it but I will anyway.

Iodine is useful in making explosives and drugs. There is a lot of incorrect information about how it can be made from retail materials on the web. Some of the published methods don't work. Others work but are inefficient and expensive. Interestingly about the only accurate description of how it can be made is from a US government web site which then says the method does not work very well and is dangerous. This is despite the method being used commercially in the quality control analysis of a well known material in almost every house. One day I'm going to publish the method on a web site and see what happens.

[havoc]

I just bought a bottle of "Carr's metal black" to blacken whitemeal and steel (according to the label) There is a large sticker on it "TOXIC Selenium dioxyde".

[ron]

Viffer
I worked for Nobels' Explosives for 35 years, it's amazing what you can get a bang out of , I don't think Iodine wouldn't be high on my list of ingredients, there are a lot of easier materials on the market
Ron

[JohnP]

Are you sure they are 7BA screws in a Victorian piece of equipment? I thought BA came in around 1910?

But I'm willing to be proved wrong!

JohnP

[paul]

One method that was 'traditionally' used by forgers to age fake medieval armour was to burn it (I suppose heat substantially would be the same) and then bury it! I suppose it depends how quickly they want the screws!!

[chris vine]

How about gun blue from a gunsmiths?

Of course I expect the police will pay you a visit just in case you have a gun. They will then suspect you are leading them up the garden path when you explain about your mate's clock. "A likely story sonny " etc etc.

They might not pay you a visit of course, just in case they were right and you did have a gun for the blueing stuff, it would be much easier to harrass a few motorists doing 31 in a 30........

Sorry that's enough of being a grumpy old git for now!!
Chris.

[the_viffer]

ron said:

Viffer
I worked for Nobels' Explosives for 35 years, it's amazing what you can get a bang out of , I don't think Iodine wouldn't be high on my list of ingredients, there are a lot of easier materials on the market
Ron

Ron

Almost a snap. I had DuPont explosives as a client for mnay years.

Iodine is rather sought after for the illicit manufacture of amphetamine and "nitrogen triiodide". I agree NI₃ isn't an explosive you'd use for a large explosion but it has a following among those who don't know better.

[districtgrandmaste]

Thanks for all these

John - actually the original is a Thurry thread 53tpi but no one stock them anymore (unless somebody knows different!) so I'm 'to teach the threads manners' as LBSC would say!

I will risk a visit to a Gunshop - if that is negative I'll work through the other suggestions and tell everyone how I get on!

[alanstepney]

Actually, BA was based upon the Thury thread.

[districtgrandmaste]

Just to close with thanks to all respondents.

Ron's suggestion of old engine oil has been successful. I went to the local garage and came away clutching a jamjar of oil from the sump of a diesel. A bit of heat on the screw and into the oil - Result excellent!

[the_viffer]

Used engine oil is not good for you. Be sure to keep it off your skin and wash well after using. Glad you are sorted tho'