My latest copy of Australian Shooter magazine contains an interesting article on the resurrection of an old alloy in a new application, for chamber casting - a bismuth alloy "originally developed for casting toy soldiers". It is marketed as Cerrosafe Alloy and is available from some US shooting supply shops (and no doubt in some other countries as well). It is a close relative of Wood's metal which used to be quite a hoot - tea spoons made of the stuff would melt in a fresh cup of tea. Being mildly toxic, I'm not sure how Aunty Hortense would take to such a trick (oh well, she was getting on in years anyway). It was actually somewhat before my time, I only ever heard about it ... honest.
Anyway, with a melting point less than that of the boiling point of water it simplifies the business of making reasonably robust castings immeasurably. Other methods in gun-smithing rely on lead slugging (best for bore and lede gauging only, really) and molten sulphur was once used for the whole chamber - but of course that tends to catch fire in the open air. So, the new-old alloy is about ideal, especially since it initially contracts slightly on cooling before slowly expanding again. Supposedly maximum contraction occurs half an hour after pouring which is the ideal time to remove it from a mould, rifle chamber, etc. It returns to the precise size of the mould after about an hour (the time to take precise measurement and for gauging) and continues to expand to a maximum of about two and a half thousandths of an inch oversize per inch after some hundreds of hours.
Now I would be astounded if the exact times are precisely reproducible but I made the following chart from the table found in one of the sites located by Googling Cerrosafe. Anyone thinking of using/trying the stuff should shop around. I checked prices at just two sources - one was US$46 per pound, the other US$85. Available in half-pound and one pound ingots.
Wood's metal which used to be quite a hoot - tea spoons made of the stuff would melt in a fresh cup of tea.
I remember Candid Camera doing that stunt on punters in a cafe. Wood's Metal contains lead and cadmium - with hilarious results. I know Health and Safety wasn't up to much in those days, but they must have used Field's Metal, which is, I gather, a non-toxic alternative. Mustn't they?
This is excellent news.
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I remember Candid Camera doing that stunt on punters in a cafe. Wood's Metal contains lead and cadmium - with hilarious results. I know Health and Safety wasn't up to much in those days, but they must have used Field's Metal, which is, I gather, a non-toxic alternative.
Perhaps they did James, but OH&S keeps raising the bar so even that might be considered risky these days. But at least systemic poisoning might be more visible should it occur - I seem to recall that severe cases involving Indium turn the skin and the whites of the eyes a bright blue (or perhaps that is just a myth put about by a particular novellist - anyway there is little/no evidence that such levels can be achieved by ingestion of the elemental metal).
Ah but it was a more carefree world then - we played with mercury as if it was water (the old silvering of the penny trick) and manufactured various explosives at will. Nitrogen triiodide (NI3 - "touch powder") being the run-away favourite. I recall our young and exceedingly well-formed lady PT teacher jiggling and stamping and screaming in rage in an altogether fetching way as the distinctive supersonic "crack" greeted her high-heels each time they hit a particular patch of mined paving in the school quadrangle below, watched from the balcony above by an appreciative audience. A physical training specialist who wore high heels (and makeup)? Says it all about those halcyon days, eh?
...I seem to recall that severe cases involving Indium turn the skin and the whites of the eyes a bright blue (or perhaps that is just a myth put about by a particular novellist...
I don't know about Indium but colloidal silver can cause cases of Argyria where the skin turns a rather zombiesque shade of blue-grey.
-- Edited by Mark Hansen on Wednesday 6th of April 2011 12:32:53 PM
Mark Hansen wrote:...colloidal silver can cause cases of Argyria where the skin turns a rather zombiesque shade of blue-grey.
Spooky, the eyes especially - so that's where the SFX makeup artists got their inspiration. Gold is apparently no problem though (no photo-reactivity). Bit off-topic but it's a sort of chemist's/medical scientist's/pharmicist's "in" joke:
There is at least one Biblical account going as far back as 3,500 years ago describing an aqueous dispersion of colloidal gold, prepared by comminution and administered to hundreds of thousands of subjects as an anti-stupidity remedy without ill effects. (http://findarticles.com/p/articles/mi_m0FDL/is_3_15/ai_n31214887/pg_2/?tag=content;col1) - refer Exodus 32:19-20 (KJ).
Back on topic. Meant to mention before that Cerrosafe could probably also be used for low-temperature soldering. Not ideal, since it only starts to "clench" after an hour but it could possibly be used in contact with all sorts of materials that would be damaged by excessive heat and/or would not "take" to normal solder. The manufacturers make other alloys for that purpose but Cerrosafe might do in a pinch.
-- Edited by Rectalgia on Wednesday 6th of April 2011 05:42:05 PM
