Back to Ganoksin | FAQ | Contact

[again] bombing


I have a question…About 14 years ago we used to do alot of
bombing of gold and diamonds. Well I cannot remember how and what
fomula’s and ofcourse it is not a play toy sort of thing.
Help me out!!! I need fomula,what chemical’s ect… Thanks


Given the number of beginners who read this, It’s appropriate to note
that bombing is potentially a highly dangerous technique. And it
generates both fumes and liquid wastes that need to be dealt with

That said, the basid process is to mix a bath of hot (I used almost
boiling) water, with cyanide. Sodium Cyanide works, but I prefer
potassium cyanide, as the resulting reaction seems a bit stronger and
more effective. As I did it, the mix was about a teaspoon of cyanide
to about a cup of water. Or thereabouts…

To this, you add a bit of 30% hydrogen peroxide. The mix fizzes
increasingly for a few seconds, and then “bursts”. That burst,
depending on the nature and amount of the gold, as well as the exact
mix and temp of the reagents, ranges from a gentle but sudden increase
in the fizzing, with some extra foaming and stuff, to a sudden pop
that’s pretty much a slow speed explosion. I do this in a large
plastic pitcher, about a half gallon size, and it can literally shoot
the foam across the sink (It’s a completely enclosed sink, to avoid
splashing and control fumes) with enough force that you feel quite a
pressure in the reverse derection on the pitcher. The point here is
that this reaction varies a good deal in what it does. If you use
more dilute or cooler reagents, the reaction is much slower, often
just a bit of increase in the fizzing and a change in the solution’s
color. This will be highly effective still, in cleaning the gold
surface, but I’ve found the harder, higher intensity “pop” to be
important in giving a good polishing/brightening effect.

Please consider all aspects of what you’re doing, though, before
doing this. You’re starting with enough cyanide to kill several horses
and you besides. And now you’re adding an oxidizer that’s strong
enough to cause severe burns on contact. (concentrated peroxide is
NOT nice stuff. Be really careful with this reagent. In some
situations, on some surfaces or materials, it will literally cause a
fire.) anyway, you’re mixing these two potentially lethal materials
and causing them to experience a violent reaction that is not always
completely predictable in it’s intensity, and which can throw that
nasty soup all over the place. In short, don’t do this in your
kitchen just to see how it works.

That said, I’ve met many jewelers who do this fairly routinely. They
do it (And I used to as well, when I worked for one such firm) just
with a simple pitcher or glass coffee pot sort of thing, often just in
the shop sink without special ventilation or safety precautions. I’ve
never heard of anyone having a real dangerous problem with this. But
I sure can imagine it happening. And environmental concerns about the
waste product should not be ignored. Also, the fumes released by the
reaction are not so pleasant. The stuff smells terribly, and can give
you a pretty good headache. I’m told by one chemist (I’ve no idea if
this is actually true, it was just a guess) that the fumes are mostly
steam, and the annoying smell is some sort of alkalinity reaction, not
actual cyanide mist. I’ve no idea what the truth is, but I suspect
the boiling and violent nature of the reaction is, indeed, putting a
steamy mist containing a tad of cyanide and/or peroxide in the air,
and that this is the source of that headache… We used to put up
with the discomfort and bother simply because the results obtained by
the process are, simply put, just astoundingly useful for some types
of work. Bombing, unlike electrostripping, reaches into all surfaces,
recesses and high spots alike. It can leave a wonderful sheen/low
polish on surfaces you could never reach any other way. Take worn
dingy tarnished old hollow rope chains and bomb em, and poof, they
really do look like showcase new, though still worn. The finish you
get really is quite wonderful. It varies a bit from gold alloy to
alloy. 14K standard yellow alloys seem to work better than higher
karat. Rose gold doesn’t seem to brighten up as well, sometimes
getting “etched” with a crystal finish. Same with some 18K alloys.

The residues, by the way, should be saved. When the cyanide hits the
gold, it starts dissolving gold, and the peroxide helps it remove even
more. The waste liquids will contain significant gold, if saved over
time. Also, note that the reaction basically is the oxidation of
cyanide to cyanate. The waste liquid is not quite as dangerous/toxic
as actual cyanide, but cyanate is still not something you should just
rinse down the drain, even though many of the aformentioned jewelers
I’ve known did exactly that.

Peter Rowe


Dear Chip and Kim

The only bombing (stripping gold etc) I know is dangerous and usually
ends up with cyanide being tipped down the sink. Which is not good
for anyone. You would be much better making an electro stripping bath
saving the solution and getting it refind by someone qualified to do
it. Bearing in mind anything to do with cyanide should be treated with
the greatest of respect and stored in a safe place.

Chris Hackett



I had a jewelry instructor once who gave, as a first assignment, a
design for a piece done bombe’. At first I thought this was what
you meant when the query first appeared on Ganoksin, but apparently
not. I never did find out what bombe’ was. I approached the
instructor before the next class, after I had done research on the
word and asked people about it and had gotten many, varied answers.
Without giving you a long story, the instructor blew me out of the
water and I subsequently dropped the class with no further adieu for
this sad (however reputable he was said to be) man who dared call
himself a “Teacher.” I was registered for another lecture class that
this instructor was giving, and I stayed in that class. I still
hold, based on that experience, that this person had no business
calling himself a Teacher, given all the knowledge it was obvious he
had and could have imparted to people who were willing to listen and
learn, but instead was rude and unkind, abrupt and supercilious, even
abusive. Given that, I was wondering if now, FINALLY, some six years
later, someone on Ganoksin could tell me what bombe’ is?
-Madeline/Arts Umbrella Studio


Madeline, I have made bombes, They are different kinds of ice
cream molded into a stainless steel bowl. Set up in the freezer
then unmolded and decorated, If you mold the green ice cream on the
outside, then fill with raspberry ice cream mixed with chocolate
morsels. when it is unmolded and cut in slices it looks just like
watermelon, what all this has to do with silversmithing I don’t
know, except is would cool you off after being on the torch all day. Susan


Regarding cyanide bombing:

For safety, cyanide bombing is often done is a special cabinet which
contains the fumes, etc. I know at least one company makes a very
small cabinet especially for small shop, called the “Lil’ Bomber” It
includes containers for the cyanide and peroxide, electric heater,
rubber port globes, a safety shield, and ventilation. In 1997, it was
offered by a company called Coating Specialties Inc. in Providence,
phone (401) 725-8910. If that doesn’t work, try Cleinman-Cooper
Technology, Inc./C.C. Tech, Inc.,in Cranston, RI 02910; 401-784-6168;
e-mail I’m sure there are other manufacturers of
similar equipment as well: try contacting your equipment supplier or
check out the MJSA Web site at for equipment

It doesn’t pay to be careless with something as potentially lethal as
cyanide. If you’re going to do bombing on anything like a regular
basis, I’d think it would be most worthwhile to invest in appropriate
safety equipment.

Suzanne Wade


Hello Peter!

Sounds like a shop I worked at also! We bombed, bright dipped, acid
etched, tumble finished emblematic pieces. Several metals were cast
and stamped, as well as gold and silver.

Knowing the value of this process and the dangers to health it poses,
I have devised an easy, small shop, one person method. Here goes. Go
to the drug store and buy a pint of 3% hydrogen peroxide. On sale
they are under a dollar. One pint is enough for 3 separate projects.
Great for keeping cuts from infection too. You will need to purchase
granular potassium cyanide. Yuk! This stuff is worse than a gun!
Don’t open it, look at it, or smell it. Only have it open when you
are using it. This is one chemical you don’t want to have any
accidents with. So don’t drop it! Just a few parts per million in
water is enough to kill birds and other creatures. Contain and
dispose of properly! Leave it in a locked (then get one) cabinet in
its’ original container when not in use.

Now really here goes. You will need to do this outside or under a
strong hood; low density, high volume. Not your $40 dollar range hood
from the home improvement store. On the West coast doing this in the
winter occasionally is no big deal. Plan ahead and be safe and
contained where you do it. Here are the other things needed in a
list: five gallon chemical approved container with screw cap. (for
waste) plastic tub 15’ diameter minimum (to completely contain the
process) 3.5 quart stainless pan (don’t use for anything but this
procedure after) 1/2 gallon pitcher with hot tap water (for rinsing)
funnel with at least 6" diameter stainless steel ring tweezers or
plastic implement electric hot plate insulated rubber gloves -
Chemical supply or garden gloves work glass receptacle (pimento jar,
mustard jar) small volume

In your stainless steel pan fill to half with hot water. Pour off
about 1/3 volume from your pint of peroxide container. Put container
in the 3.5 qt. pan with lid loosened. It will float partially
submerged. Catch the lid on the edge of the pan (make a hangar for
the cap out of copperwire if you have to). Allow to come to 200
degrees. The water has bubbles, but do not break the surface or boil.
That is plenty hot. To little temperature makes the reaction take
longer, and results are not as bright.

Warm your small glass container (it will crack otherwise) with the
pitcher of hot tap water with your jewelry piece in the container.
Now fill to just cover your jewelry with the hot peroxide. Put the
peroxide aside. With an inch or so of water in the 3.5 qt.pan put
your jar in the middle of the pan. Take off the burner temporarily,
and put in the plastic tub. You do have your gloves on now. Have your
cyanide ready with a spoon. The amount of cyanide is quite important.
If you are using a pimento jar, half full of peroxide; my best
description of the cyanide amount, would be amount of volume of a
nickel. To give it a number my guess would be 1/8 teaspoon. Less is
better your first time! Don’t add to much! You WILL be wearing it!
The addition of cyanide will initiate the chemical reaction. Agitate
while boiling (the reaction). It only takes maybe thirty seconds.
Drain the spent fluid into your five gallon container, with funnel.
Rinse with hot water into container. Return pan and peroxide to
burner. Bring to same temperature. Repeat process as explained above.
if the desired surface appearance has been achieved, a second strip
may not be necessary. Too get maximum brilliance, I usually do a
second or third step this way. By watching, and timing the event very
closely, I “interrupt” the reaction when it is very nearly finished,
by rinsing the container with the rinse water. Now inspect the
results. You will notice almost a 24k appearance throughout. After
polishing the recessed areas will of course still be this color. If
that is not desired, you can use the plain water and add about a
dime’s volume of cyanide. That will reveal a color more closely
resembling its’ true karat. This “cyanide bath” is also good for
removing unwanted patinas. If you accidentally copper plate a
sterling piece in your pickle. It can be removed with a cyanide bath.
You will need to do it several times to remove the copper.

Rinse any spillage out of your tub and clean all articles used in the
process. Add the lot to your five gallon container. Put the cyanide
and waste away, locked. You never know what set of circumstances
could arise. An unknowing person or child could create a very
unhealthy situation with this stuff. Be safe!

The method described above is not to be compared with things you
could do with a rectifier. This produces a much brighter finish, than
that which is capable electrostripping.

Most pieces do not need stripping. It depends on the design. The
pieces that I choose to strip usually have gallery work, or other
inaccessible areas. Quite necessary in some of the deeply relieved,
Celtic designs, and so on. After azuring with square burs, it
virtually makes it unnecessary to polish. Always remove the casting
skin, everywhere possible, prior to stripping. The bombing (or
stripping) process is much brighter in appearance, if you have
removed the casting skin prior. I try to reach the areas with tiny
ball burs, flame burs, or tiny tapered diamond points. The piece is
completely sanded, rubber wheeled, ready for polishing, except stone
setting. It is then stripped in the method above. After stripping
the stone setting areas are then high polished. Stones are set. Then
final polish.

Those of you reading this who are unfamiliar with chemicals in your
jewelry work thus far are advised to run this method by a mentor, or
shop that can introduce you to it safely, with some guidance.

On a post a while back, I saw a suggestion to add chemical waste such
as this to kitty litter, let it dry, and send in with your other
refining stuff. That is what I would suggest, to rid of this waste
occasionally. We definitely are wise enough not to put it down our
drains, or into our ground water! As I look back that is exactly what
most of the shops did! Thank God we now realize the environmental
damage and we care enough to dispose of it properly!



It is something I don’t do any more but we used to run cold water
into the solution before the explosion took place. It takes some
experience to do this to get a good strip. Most people I have known
who do this tend to pour the final liquid down the sink. I am sure
there are a few ethical questions about this. I still think that
electro stripping is the way to go (if you can afford the equipment).
You are still using cyanide as the main agent but it is sure not as
volatile as bombing. Like many chemicals used in the jewelry trade
they are only as safe as the people using them.

Chris Hackett


madeline - i’ve always thought ‘bombe’ was a french style chest -
sort of a low slung thing with drawers that resembles bubba with a
beer belly in his skivies . actually a chest that pooches out at the
bottom in front, on stubby little legs - as i said above … ive ps:
or an ice cream dessert, but don’t give any to bubba, he’s already



as having been exposed to cyanide in an improper manner…(such as
using the cold water quench)… and the vapors it produces…(often
with the help of chlorine in the water) it is a dangerouse
material… i got contaiminated with skin exposure in 85. by 1990 I
was having surgery on my liver… now l face many other problems as
the hospital gave me hep C during the operation… If I had been
trained properly this would have never happened!!! the only way
to deal with bombing is to be upwind and outside and never be close
to the reaction container… dry the liquid to a powder so it can be
safely transported and have it refined… there is gold in that
residue… So as a word of advice… they kill criminals with it
don’t they??? and if there is any acid in the sink trap you may not
get out of the room… ringman


Bombing enjoys a good treatment in one of the Murray Bovin books:

Silversmithing and Art Metal
Jewelry Casting

(is the phrase you were stabbing at with ect.)
means “and all else” in Latin.


Hello Ringman!

Saw your post on cyanide bombing. Your experience with cyanide should
be a lesson for those unfamiliar to take every caution. My bombing is
always done outside and I very carefully position so as not to breath
the fumes. I have a small one man shop and will not put an applicable
exhaust fan in my shop for only this purpose. The number of pieces I
need to strip per year is less than ten I suppose. I have a kitchen
hood above my casting area. I know that is inadequate for chemical
vapors. Anyone who read my (10/10) post or others explaining this
technique; it can be done safely. You must be careful! If you are the
slightest bit unsure of the procedure, quantities, containment, or
other factors; get help, ask questions. This is not a procedure you
can afford your first try going poorly!

Go to the drug store and buy a pint of 3% hydrogen peroxide. 


when I was first shown how to bomb, it was with boiling water to
which one added first cyanide and then 30% peroxide. That
concentration of peroxide is truly nasty stuff. In some ways, more
dangerous than the cyanide. Yet using a less concentrated form of
peroxide doesn’t work when you’re starting with boiling water. I
know, I’ve tried even the 20 percent stuff you can get from hair
dresser supplies. Doesn’t work as well. However, your solution of
using dilute peroxide heated INSTEAD of the water, sounds great. One
could modify the peroxide concentration if desired with the beauty
supply/hair dresser concentration stuff too, and that, which is
usually 15 or 20 percent peroxide, is a LOT safer than the 30% stuff.
So thanks. I’d not thought of reversing the process this way. One
less nasty chemical to keep track of. You are also probably getting
less initial loss of gold this way, since until the cyanide hits it,
no gold is being removed. Thus the gold is only being stripped while
the active reaction is taking place, and this may well be a benefit,
just thinking about it. I’ll have to try it and compare.



Chris, The trouble with adding cold water is that it seems to lessen
the redeposition of fine gold onto the stripped surface, and that
color enhancement effect unique to bombing is then lessened. And the
polishing effect is also lessened. But it is still just as effective
at removing scale and tarnish etc.

The explosion, by the way, can also be greatly lessened by simply not
using as hot water to begin with. The reason it explodes is that the
peroxide is oxidizing the cyanide to cyanate, and as with many
oxidation reactions (burning, for example) the reaction gives off some
heat. If the solution is already boiling hot, the rise in temp causes
it to superheat, meaning it rather suddely boils over. Fast enough in
fact, that it’s almost explosive. If the water isn’t as hot to begin
with, then it’s just suddenly boiling. But the speed of the reaction
does seem to have an effect on how well it polishes, and how well it
redeposits that fine gold color on the metal. So I prefer to get a
good “pop”. I do, by the way, take care to use a loose cover over the
pitcher I’m doing it in, so the chemicals launching themselves out of
the pitcher get diverted back down by the cover, safely into the sink.
I’ve got my sink set up so I can divert the waste water to a
container instead of down the drain, and for bombing, I do exactly
that. Partly because it’s not so good to flush the waste down the
drain (the waste cyanate isn’t so bad, but if there remains unreacted
cyanide in the mix, I prefer that it not go down the drain. But
frankly, the big reason is that the mix contains significant gold.
And it’s easy to recover too. Much of it will simply settle out. The
gold is quite soluable in the initial cyanide bath, but not so much in
the end cyanate. As the reaction proceeds, just before it explodes,
the color chages to brown. That’s the gold coming back out of solution
to a finely divided state suspended in the solution, rather than as a
cyanide salt dissolved in it. This is also why fine gold redeposits
back on the metal. For a brief bit, the solution is supersaturated
with still dissolved but reacting gold cyanide, and some, instead of
reducing back to pure metal in the solution, is literally plated back
onto the workpiece…

As to electrostripping, you’re quite correct that it’s often a good
substitute. however it does work differently. As with all
electroplating processes, the degree of activity is affected by the
exposure of the surface in question. so high spots and convex areas
closest to the cathode will strip more quickly than recesses. And
interior or highly protected areas won’t strip much at all. since one
prime reason to bomb things is to remove tarnish, oxidation,
whatever, from those areas that are not otherwise reachable,
electrostripping is often not nearly as effective, since the areas you
most wish it to reach are those areas which it will not. Combining
electrostripping with the new magnetic tumblers, however, has proven a
pretty good substitute for me most of the time. Often the tumbler
will do it by itself.

Peter Rowe


There seem to be some question about the liabilities of using cyanide
in the jewelry making process. If I recall correctly some ten years
ago there were several deaths among Los Angeles Department of
Sanitation workers which were the result of Large qualities of cyanide
being dumped in the Los Angeles Downtown jewelry district. As a result
there was a large criminal investigation and several building owners
were fined and there buildings were removed from the sewage system,
until compliance could be proven. The last time I checked Again
several years ago, the use of any amount of cyanide would put one in
the Large Generator Of Hazardous Materials category, which involves
filing monthly reports of where and how all waste materials are stored
and disposed of. Personally I do not want to file these reports, so i
will not use cyanide, especially since there are alternatives.