GOLD "BOMBING" PROCEDURES AND REGULATIONS NEEDED

A. Hi Dane. I am acquainted with the "cyanide bombing" procedure but am surprised to hear that it is ubiquitous; I only saw it done twice, decades ago, and the demonstrators thought they had something pretty unique.

If it is done primarily in smaller and medium size operations, what process do larger operations use in its stead, and what precludes the smaller operations from doing the same?

You are probably correct that the waste products are harmful and dangerous, but 'toxic' is an overused politicized word and I don't like to see you use it (at least you didn't use 'spew'). In my State the governor reminded everyone that " 'toxic' is a matter of statute not opinion"; but this cuts both ways: a harmless material is toxic if the State defines it as such, and the harmful materials you are complaining about are not 'toxic' unless California and Hawaii so rule.

The plating industry is very heavily regulated and has been for decades, so plating shops don't vent this to the atmosphere nor run it down a drain. Other gold processors may, but I'd presume there is an EPA 40 CFR covering gold and precious metals works. That's where I'd start looking.

You may also want to review topic 82 here.

BUT! This operation is very hazardous for the person doing it and, if it is done at all, it should only be done behind a fume hood after you have received personal hands-on instruction and have had full accredited haz-mat training. NEVER even think about doing it from something you read on the internet!

Regards.

A. It is true that "Cyanide Bombing" process is the most preferred mass finishing process since it is fast and can be batch treated. I have personally worked with bombing of jewelry and I have to say that the word "toxic " is pushing it a bit too far. When a solution of boiling sodium cyanide is treated with hydrogen peroxide, then a large amount of gas (probably hydrogen ) is released which actually does the scrubbing action on the surface of the jewelry. Cyanide is instantly converted to a cyanate which is not considered toxic and can be easily disposed off after removing the precious metals by plating it out and treating the residual liquid with bleach ⇦ bleach/sodium hypochlorite in bulk on eBay or Amazon [affil links] to ensure proper removal of any cyanide present in the solution.

I am not aware of any specific OSHA regulations for this process but a proper enclosed area like the sand blasting unit with a ventilation leading to a scrubber should suffice the proper precautionary measures. The operator should have proper rubber gloves ⇦ this on eBay or Amazon [affil links] and eye protection (goggles ⇦ this on eBay or Amazon [affil links] ) while working with these chemicals.

The word "bombing" sounds like something very toxic and hazardous but in fact the reaction causes some frothing and bubbling causing some liquid to jump out of the container due to rapid release of gas. Please let me know if you need anymore information. I would be happy to direct you to somebody who actually uses this process and help you in this matter.

A. I am a 4th generation goldsmith from Sweden, I learned from my grandfather.

We used potassium cyanide with hydrogen peroxide all the time, and this was the process as I recall it. Please forgive me if I don't know the right terms in English, I learned all of this back home in Sweden :)

1) After assembling the piece, put it in heated (diluted) sulfuric acid until all the black spots and all the borax (or whatever you used) is gone. Word of caution: Don't heat the acid at the same time as you're heating the cyanide...

2) Rinse, dab dry, and polish on the wheel with the rougher compound.

3) Put the piece(s) in an enamel pot with enough cyanide mixture to cover it. (I would guess we used maybe half a deciliter of cyanide in about 5 liters of water. We had "the scoop" and "the bucket", and I never had a reason to know the exact measures - sorry! We did mix it beforehand and used only what we needed each time) When the cyanide is boiling, turn off the heat and pour in a dab of peroxide (somewhere in the 30% range concentration-wise, so not the peroxide you get at the grocery store) and QUICKLY move your pan to where it can bubble up and "boil over" safely. We used a drum with a funnel. The contents of the drum were a very pretty blue :)

4) Rinse and dry, and polish on the wheel with the finest compound.

5) Wash in heated ammonia ⇦ this on eBay or Amazon [affil links] and dish washing liquid (we used Fairy - a squirt into water enough to turn it a light green, and then a bit of ammonia - couple of tablespoons, probably. Here also, just enough liquid to cover the pieces). Don't let the ammonia boil - you'll smell it anyway ;)

Feel free to get back me if you have any questions - or any answers for that matter - I'd love to find out where I could get this stuff, as no polishing method I've tried in this country even comes close...

Thanks,

//Gunilla//

A. I am head of a jewelry manufacturing unit in India. We use bombing for improving finishing of jewellery. For recovery we were using electrolysis method. However recently there is problem in recovery. it may be due to high silver content in the liquid waste. Someone told me there is another method which uses addition of HCL. Can somebody explain details of the process using HCl for recovery.

A. Hi, I do the "bombing" method you describe. I too do not have the exact quantity measurements! Mix about 1/2 - 3/4 cup of cyanide to approx. 5 liters water. The water should be about 70 °C temperature, stir to dissolve cyanide. Put item to be stripped (bombed) into a dish - I use a Pyrex dish - and add about an egg-cup full of hydrogen peroxide. Take care to keep your face away as this mixture is volatile and you don't want to be sprayed by the explosion. Wash out with clean water as soon as reaction is complete. If there is any oxidising of your treated item, just soak it in the cyanide solution for a bit and it should come out clean. After a bit of practice, you will work out the method and quantities to best suit your needs . I test the temp of my water so the reaction times are consistent.Good luck.

A. I read a posting talking of combining Cyanide and ammonia ... I was taught that this combination should always be avoided, cyanide and ammonia should be stored in different rooms.
Bombing [cyanide/peroxide] to the full explosion has been explained in previous posts, but if you require a totally brilliant finish [especially to inner surfaces that can not be polished or tumbled] to item[s] it is necessary to go a step further -complete the full bomb, then 2 or 3 times place item in the hot cyanide, then introduce a small amount of peroxide while giving the container a vigorous swirling motion, then kill the mixture with cold water BEFORE the full explosion is completed.
Practice on an old item to perfect the system.
I have used this extra stripping process after bombing for over 40 years and still have companies send items to me where the gold looks dead and needs some life with never any complaints.

There is one thing that 'Bombing' your castings does that beats electro-stripping ... it can kill you much faster.
I'm 57 years old, and have seen the most inexperienced goldsmith do this technique at home in his basement, without exhaust ventilation and in a plastic basin. I have also seen a professional shop situation with 12 employees do this technique, and both eventually go back to the electro-stripping method.
Stop fu##!ng around with this s#!t.