[Jewelry making - Article 00058] - Re: [Orchid] What is Jewelry bombing?

[Peter W . Rowe]

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>     Happy new year to one and all. I am new to this forum and am
>     enjoying reading all the responses I have tried to geather
>     information about jewelry bombing I know it is a reaction between
>     caynite and hydrogen peroxide but in what percentages and what do
>     you do when it goes out of control 

    Well, first off, be sure you understand the dangers. Your spelling
    of cyanide as "caynite" makes me wonder if you should be near this
    stuff. If it's just a language translation problem, then OK. If not,
    be sure you're well educated in the use of these before going near
    them, for your own safety, and that of others around you. 

    One chemical used, hydrogen peroxide, is usually used in pretty
    strong form, ie 20 to 30 percent (unlike the almost miniscule
    percentages used in pharmacy "disinfectant" types.) At these
    strengths, it's a powerful oxidizer. I've never seen it start
    something on fire, but am told that's possible. And I HAVE seen a
    spill of it leave what appears to be a pretty good burn mark on a
    wood table top. Certainly, even brief contact with skin can leave a
    painful burn. 

    The second chemical, is either sodium cyanide or potassium cyanide.
    Both are lethally dangerous if mishandled. Contact with acids,
    especially, releases colorless hydrogen cyanide, a lethal gas with
    only a mild odor that killed it's discoverer, and used to be the
    killing agent used in gas chamber executions. Generally, when
    accidentally produced, the gas can kill those around before they even
    realize there's been a problem. This is not something to play around
    with casually or without proper equipment. Without contact with
    acids, of course, both chemicals are widely used in electroplating
    baths, and metal cleaning processes in industry, but again, this
    isn't something to use casually. Ingestion of even small amounts can
    be quickly lethal (seconds or minutes). Less than half a gram of the
    stuff can kill you, and much smaller amounts can do damage. And even
    when used safely and sanely, cyanides pose environmental risks when
    disposed of in waste waters if not properly neutralized first. If
    you're using it, you no doubt face a wide array of various government
    regulations on how it can be handled, stored, and disposed of. 

    Then there's also the observation that today, with modern
    electrostripping solutions, or the advent of modern tumble finishing
    methods, often there's no real reason to "bomb" anything, since
    similar results can often be attained by safer means. 

    If, after reading all my prior warnings, you're still keen, then
    here's my experience, from years ago, back when I was still stupid
    enough to do this. I worked for an employer in a very small studio,
    and she'd learned this from some old jeweler she knew or something.
    She felt that since it hadn't killed her yet, nor anyone she knew, it
    must be safe enough. I was dumb enough to go along, and fortunate
    enough that the worst I ever had to show for it was a splitting
    headache. No doubt, I was very lucky. 

    We use bombing mostly for things like chains, hard to clean up and
    buff otherwise (this was before magnetic tumblers). It worked best
    for us with 14K yellow gold. white gold would get a frosty finish,
    and 18K often would get a slightly frosted look with the crystal
    structure of the metal etched in, though not enough to be a good
    attractive "crystal" finish. but it left 14K yellow gold bright, a
    richer yellow color, and unlike plating or electropolishing, the
    finish was even all the way into all recesses and interior areas. 

    We used a plain plastic half gallon pitcher for this, though
    sometimes I'd used a covered glass coffee pot sort of container.
    About a half cup or so of water was held so the nozzle of our steam
    cleaner was fully immersed in it, and the foot pedal held down until
    it was boiling (Like steaming the milk for your latte. much faster
    than boiling it any other way, but other ways would work fine.) Had
    to be boiling. In would go the jewelry, where it would be joined by
    about a teaspoon of potassium cyanide powder (which seemed to produce
    a faster more energetic reaction, which we felt gave a better result.
    This would amount to a total mass of less than a cup of stuff in the
    bottom of the pitcher. We'd swirl that around for a moment, and it
    would by then have dissolved the cyanide and be lightly cleaning the
    metal. Then in would go a small bit of peroxide. We didn't measure
    carefully. Just pour from the bottle. Call it a "glug". Likely the
    volume was about two tablespoons perhaps. Just a litle bit, at any
    rate. The pitcher would now be lightly swirled, all the while being
    sure to hold it at an angle pointing well away from oneself, towards
    the back of the sink or bucket in which we did this. A high back wall
    right next to the sink or bucket was and is essential. You could stop
    it at any time by adding cold water to dilute, but we didn't. First
    the mix would lightly bubble for a bit, increasing in intensity,
    then suddenly it would "burst". Almost an explosion, but without much
    force. You'd feel a bit of a bump on the pitcher, and the mix would
    froth up from the bottom of the pitcher in a rapidly bubbling and
    steaming mix. Mostly you'd need to expect it, so as not to be startled
    into dropping the pitcher. The reaction would vary some (due no doubt
    to our imprecise measurements of chemicals) from a fairly gentle quick
    frothing up that stayed in the pitcher, to a pretty sudden burst that
    could shoot pretty forcefully out of the pitcher, which was why it
    always was aimed at the back wall of the (deep) sink in which we did
    this, so as to catch it all without spilling or sending it all over.
    The result was then rinsed in hot water. If we wanted the final deep
    pure gold color, it was done. If not, we'd leave a bit of hot water in
    there, and add another pinch of cyanide powder, which would quickly
    remove that deep pure gold surface color, leaving the same bright
    color in the actual color of the alloy. 

    Now, Having written all that, i can just imagine much of the
    readership of Orchid cringing, either at the safety risk, or the
    realization that the waste product was going down the sink drain.
    Neither was good, but like I said, I was a lot younger and dumber,
    and it was the way my boss did it, so it was the way I did it. For
    what it's worth, my late father, a research chemist by trade, had
    heard this process described by me, and didn't express outright
    horror, only hope that I knew what I was doing... (great patience
    there). And this IS, for better or (mostly) worse, how a lot of folks
    used to do it. In an edition of one of Murry Bovin's books from the
    '70s, he describes pretty much this same procedure. So there's a
    certain tradition to this method, safe or not. 

    I like the actual results of the process. Unlike electro methods, it
    doesn't affect high spots more than low, and when it works right,
    it's a very nice uniform finish. If you don't like the results, just
    repeat it and see if that's better. it's very quick to do. 

    The downsides, well, you're handling, as I've mentioned, two
    potentially lethally dangerous chemicals, and maybe, if doing as I
    described, doing it recklessly. Better would be to do this in a fully
    enclosed lab hood, with good ventillation so you're not breathing the
    fumes. it doesn't generate lots of specific fumes, but there IS
    steam, and that will carry some of the chemicals with it, so you DO
    get some exposure. Enough, as I've said, to give me a pretty nasty
    headache a couple times. And if the "burst" goes out of bounds,
    you've got a toxic spill to clean up. Not good. Second, from the
    moment the cyanide hits the gold, it starts dissolving gold at a
    fairly rapid rate, and the peroxide speeds that up. If you bomb stuff
    a couple times, you'll find the removal of metal from the surface
    reaches measurable levels. So that brown yucky waste liquid contains
    enough gold to be very much worth reclaiming, and you're jewelry is
    getting ligher in the process. Don't just throw the waste away. In
    addition to gold, it will contain both traces of cyanide that maybe
    didn't fully react, and the portions that reacted with the peroxide
    to form cyanate, which fortunately, is less toxic than the original
    cyanide. The whole waste product is still not safe, nor safe or legal
    to dump down the drain. 

    Were I doing this again, a couple additions would need to be made to
    this process. First, for safety, I'd want to do this in an enclosed
    "glove box" type thing, so neither fumes nor liquid could reach the
    outside or the user. Good ventillation with chemical fume filtration,
    exhausted to the outside would be added. There are commercial units
    available specifically for this process. They include carbon filters
    and a cyanide destruct unit that first reacts the waste with acid to
    destroy any cyanide, while then filtering out and trapping the
    produced hydrogen cyanide gas. Needless to say, this should not be
    equipment you build yourself without a good deal of chemical
    engineering background, but were I doing it, I'd skip the cyanide
    destruct unit, opting instead to contain the still dangerous waste
    liquid for seperate processing later. And that would be the other
    main addition to what I once did. Nothing goes down the drain. It all
    gets saved. The resulting brown waste liquid can be neutralized and
    it's gold reclaimed. You'd want to consult with your refiners to
    determine the best method of doing that for your own situation. 

    As a final note, please consider using this posting as informational
    data only, rather than instructions you should follow. The procedure I
    knew and used is one I do NOT consider safe, nor the best way to do
    it. Certainly, in industry, when it's used properly, it's different
    from this. Commercially used bombing stations, when used as intended,
    don't normally have to contend with that "bursting" or explosive
    effect, yet still get good results. And they do it a whole lot more
    safely than the method I described. Don't ever forget that done
    wrong, this is a highly dangerous method. Just because some oldtimer
    jewelers may have done this now and then does not legitimize it or
    make it safer. I'm not just being a politically correct prude here.
    This really IS potentially dangerous stuff, OK? Be SURE you're
    properly equipped and educated before doing any bombing. This posting
    has not done the educational part sufficiently. 

Peter Rowe

 
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