Nitric for silver etching

Jewelry Discussion
1

Good Morning Orchid-Land!

I have read & researched the blogs, and cannot find the exact answer
I am looking for, so I thought I would just stop wasting my time and
ask:

I need to do some silver etching with Nitric acid. I have found a
few sites online to make the purchase, (the shipping is a tremendous
amount of the cost due to its hazardous nature), but what I have not
figured out is what concentration I need for my etching purposes. I
can buy the concentrate, which is 69-71%, for a relatively reasonable
price. The amount I need is probably about 500cc. My concern is not
storage, I have a cabinet, (vented) in the garage that I can lock,
and I can etch under a hood, wear my chem-mask, gloves, etc. to make
it safer. I have used Nitric before when in school, and understand
the safe usage, hazards, warnings, etc. (I take safety very
seriously.)

My biggest concern is that I don’t know whether to dilute it, or just
go ahead and use it at the strength it comes in. At University we
always got our acids from the chemical storage at our college, and it
was what they called “spent”, meaning used, and I would assume less
concentrated. Will a 70% solution be too high? If I order 500cc and
dilute it will I have a TON of the stuff left over to store forever?
I would like to keep it on hand, but I don’t need enough to devour
the world either, lol. I am pretty certain that there are jewelers
out here who do silver and gold etchings, so I am asking for some
educated advice. Any help here would be greatly appreciated before I
place my order. THANKS!

Teresa

2 
I need to do some silver etching with Nitric acid. I have found a
few sites online to make the purchase, (the shipping is a
tremendous amount of the cost due to its hazardous nature), but
what I have not figured out is what concentration I need for my
etching purposes. I can buy the concentrate, which is 69-71%, for a
relatively reasonable price.

I personally mix mine to approximately 25% strength. I didn’t like
the cost of the available nitric acid and its shipping costs, so I
purchased mine from a hydroponics website. It was sold as “Nitric
acid pH down”. That confused me at first, as I thought it was some
sort of mixture of nitric acid and sodium bisulphate (as sodium
bisulphate is often sold as “pH down”), but it is just a 38%
solution of nitric acid, which I then dilute down to 25%. There were
no outrageous shipping charges, and it was a reasonable price itself.

Even better than nitric acid is ferric nitrate, which comes as a
solid, in granular form. It etches more cleanly than nitric acid,
which tends to be too aggressive and produces a really blotchy etch
with no clean details.

It sounds like you already know how to achieve the required dilution
(if you do indeed want to use nitric acid rather than ferric
nitrate), but if help is needed to calculate diluting from 70% to
25%, for example, then just ask offline and I’ll give a detailed
breakdown (I’ve been criticised for giving such advice on forum in
the past).

Helen
UK

3

Hi Theresa,

My first question is what are you etching and why do you need nitric
acid.

Silver etches great with ferric nitrate. If you need assistance in
quantities for etching or assistance with a good and proven protocol,
email me off line.

karen christians
cleverwerx

4

The conc nitric you have will be too harsh for etching and will
leave a coarse finish. You need to dilute it to about 25% by adding
150ml acid to 350ml water. Do this slowly as it will exotherm
something terrible if you just throw it all in at once. A lesser
dilution will work but just a little slower, which will give a leass
coarse finish to the etched metal. I use 100ml to 400ml water and
this works fast enough.

Nick Royall

5

Teresa,

Where do you live? I have a large bottle in my garage. If you lived
near me you could have it. Maybe some one lives near you and they
give you some or sell you some. That way you save on shipping and do
not have a ton to store. Just a thought. Sorry I can not answer your
question. I have never used the stuff. It was at an auction. When I
told the people in charge the stuff was dangerous and could get
knocked over by the kids running around they handed it to me and
said take it away. Maybe one day I will use it for something.

John
Grand Junction, Colorado

6

Depending on how aggressive an etch I want I dilute the concentrated
acid with 50-75% water. So for a fast etch I use 50/50 concentrated
acid to water and for a slower etch I use 25/75 acid to water.

Jim
James Binnion
James Binnion Metal Arts

7

Hi Teresa

Let me give you a quick background of my etching experience, in case
you wonder. The metals Department and the printmaking department
were adjacent to each other so it was very easy to use the facilities
there while in school. I do not etch anymore. After school,I used to
run a production line of etched silver and gold fusion line in the
80’s and 90’s. The fusion technique/and look was big then. I had
purchased one 16 ounce bottle of nitric for about $5.00 from our
jewelry supplier in town 1983 straight out of school, at the time
did not think about how long it would last at what cost to who…
very heavy usage, and working capabilities in nitric, But at the end;
early 90’s I changed over to Ferric nitrate, it is a lot safer and a
lot nicer to the environment. but $$$ and still have to pay extra
extra for shippingas you mention at the end of your email you do not
need to have so much that could destroy the world:).

well when at the end of my production line run ; my decision was to
neutralize the concentrate nitric I had, it took about 20 + pounds
of baking soda to neutralize and running water for about 3 hours, to
completely neutralize the 16 fl ounce bottle of nitric. usually it is
very high concentrate I think this was 80-to 90% that is available
and it is cheap. VS the Ferric where it was $18. 00 for 16 flounces
that would last about 3 or 4 sessions. with the nitric you need to
dilute, start weak you can always go stronger bit by bit, but you
can not go back once your metal is etched and gone. also when the mix
is weaker, your resist, what ever you are using will stay on better
or longer. even with the 60 or 70% I would start with a 30 to 1
dilution. keep good records of that, maybe test pieces also.
Temperature plays a huge role. one day I noticed in winter that it
was taking very long to etch, finally figured out that the cold
weather had cooled down the acid, and was giving me a hard time. SO
i got this brilliant idea to warm the acid… it worked amazingly
well. till shortly after I found out that the Yellow vapor that was
coming off the mixture and falling down to the ground, (vapor heavier
then air?) was apparently Mustard Gas… stopped me dead in my tracks
with that practice.

I have always considered my self pretty safety consciences, but when
you don’t know, you just don’t know till it may be too late. as for
storage, I found that there was no material strong enough to hold the
nitric safely stored indefinitely, I did have a chemical safe
cabinet, but everything else in it seemed to disintegrate just by the
vapors coming off the closed bottle top. that had also disintegrated
a few years into storage. I would suggest buying as little amount as
possible. or just go to the Ferric nitrate family. My advice is to
find another technique to get similar results, some of this stuff we
use is just too damaging to the planet. some thing to think about. I
gave up my line and went to another technique all together.

Hratch Babikian

8

I use ferric Nitrate for etching my silver. The PNP which I use as a
resist holds up well in the Ferric Nitrate. I buy the Ferric Nitrate
dry in lump form and mix whatever I need. It is much safer than
Nitric Acid, and I get an excellent etch with it. No fancy expensive
equipment needed.

Alma

9 
You need to dilute it to about 25% by adding 150ml acid to 350ml
water.

Not meaning to split hairs, but using a 70% strength acid to start
with (as the poster stated), this gives a 21% strength final
solution, not 25% - but it’s close enough.

I use 100ml to 400ml water and this works fast enough.

And this will give a 14% strength solution.

So for a fast etch I use 50/50 concentrated acid to water and for a
slower etch I use 25/75 acid to water.

The above quoted from another poster. That’s fine, but the original
concentration is NOT stated, unless again it is the original
poster’s 70% which is being talked about.

It drives me insane when people state ratios of solutions to water,
but they don’t state what concentration solution they are starting
out with. We can all buy solutions of varying concentrations, so I
feel it is important to state the concentration used when stating
what ratio to mix it in.

I’ve said it over and over again, if you want to mix a solution to a
specific concentration, then use the following formula and
substitute the numbers. It works both ways round, ie you can state a
starting volume of acid and it will tell you how much water to use
(by subtracting the acid’s volume from the final volume), OR you can
tell it what volume you want to end up with, and it will tell you the
volume of acid to add (which will then be made up with the remaining
volume of water, again found by subtracting the acid from the final
volume).

Original Concentration X Original Volume = Final Concentration X
Final Volume

It will obviously also work if your unknown is the final
concentration.

Helen
UK

10

Please can people state what concentration they’re talking about,
when quoting a ratio of acid to water (or any similar answer to a
dilution problem). We can all purchase various concentrations of
acids, etc, so it is important to say what strength you’re referring
to.

Simple formula for dilution is as follows:

Original Concentration X Original Volume = Final Concentration X
Final Volume

Just input the numbers - it works which ever way round you use it.
You will need to decide either the volume of acid to start with, and
it will tell you the total final volume, OR you can decide what total
final volume you want to end up with, and it will tell you how much
acid to start with. REMEMBER though, that either way, you will then
need to subtract the starting acid volume from the final volume to
deduce the volume of water needed. And remember to add acid to water
rather than the other way around.

Helen
UK

11

Teresa,

I use a 1/5 solution of nitric when I etch (one part of nitric acid;
four parts of water) and this works very well and very fast. A 70 per
cent solution will work too, but it is not necessary and you need to
take for spills. Why don’t you give it a try and then dilute it or
not?

Regards,
Alicia

12 
it worked amazingly well. till shortly after I found out that the
Yellow vapor that was coming off the mixture and falling down to the
ground, (vapor heavier then air?) was apparently Mustard Gas...

Not from Nitric Acid - Mustard gas was Chlorine… however, the
brown gas from Nitric acid is just as toxic and is very corrosive…

Ian
Ian W Wright,
Sheffield UK

13 
Please can people state what concentration they're talking about,
when quoting a ratio of acid to water (or any similar answer to a
dilution problem). We can all purchase various concentrations of
acids, etc, so it is important to say what strength you're
referring to.

Good point. The nitric we use at school started off at 70% (same as
the original post), then we’d dilute it down 4 parts water to 1 part
acid. I think the last bottle we got was either 60 or 65% & I didn’t
notice any difference after diluting it down the same way. Some
other students used the 8-1 solution that I mentioned for copper to
etch silver & it worked fine, it just took a bit longer. And yes-
AAA. (Always Add Acid). Much less likely for the acid to splash that
way. I disagree about the formula being easier to deal with, though,
but that’s because math is not my strong suit; I wouldn’t be able to
translate my measurements into that formula at all. It’s more
precise, certainly, but I find it’s easier to just measure out 4
cups of water to 1 cup of nitric (with glass measuring cups, natch).

I do not recommend trying any acid straight out of the bottle.
While they’re typically not at 100% strength, they’re still far more
likely to cause injury or damage at those higher levels-- not to
mention eat through your silver.

Sharon

14

Before paying the Hazmat charges for shipping on any chemical, try
calling a chem company in your area. You may have to spend an hour
tracking down a lead, but it’s worth it.

Nitric is cheap, and once you have a company with that uses it, you
should be able to get small quanties from them at a very low cost.
If it is an industrial chemical company, they may not have any
containers less than 55gallons, so bring an acid safe bottle with
you.

Plus, if you offer to bring them a sixer or brews they may dispose
of the spent acid for you. It’s worth a shot :0)

Michael Johnson
http://www.cosmicfolklore.com
http://cosmicfolklore.ganoksin.com/blogs/

15

Hello,

I also used ferric nitrate a couple of times, but I find it very slow
and the solution loses its potency to bite fairly quickly. A 20 %
solution of nitric acid on the other hand works very fast and needs
no equipment at all, except for a dish and something to stir from
time to time. Nitric acid is hard to come by over here and therefore
I use a pickling solution made by Avesta (a Swedish firm) which is
meant to be used on the welding joints of stainless steel. It
contains 19 to 15 % nitric acid and 2 to 6 % hydrofluoric acid. I
think it is quite dangerous, but I use gloves etc.

16

G’day;

---- it worked amazingly well. till shortly after I found out that
the Yellow vapor that was coming off the mixture and falling down
to the ground, (vapor heavier then air?) was apparently Mustard
Gas...

Sorry Ian; but mustard gas is not yellow chlorine, {Cl) but is a very
unpleasant complex sulphur liquid which was used in WW1 and was
termed /a lachrematory vesicant/ which simply means that tears simply
flood, and it produces nasty blisters on skin, and it is extremely
toxic It smells like a mix of garlic, mustard and horseradish. When I
was in the British Home Guard in about 1940, at lectures we had to
attend, small, highly diluted samples of poison gases were passed
around among the audience. (Britain was scared that Hitler might use
gas against us.)

I breathed chlorine when I raced down a long passageway to turn off
a cylinder of the gas which a student had left turned on, when I was
a senior technician in Victoria University Chem Dept. Wellington NZ
The only gas mask had been left hanging on the cylinder!! I lived!
(I’m 88)

The brown gas from the space above the acid in a bottle is nitrogen
dioxide and some nitrogen peroxide. The brown gas is also given off
during the copper/nitric acid reaction, Nasty, poisonous, but not
nearly as bad as mustard gas. (I have breathed that too!)

By the way Ian, I worked at the British Iron And Steel Research
Association in Sheffield for four years also. '53 - '57 We lived up
in Walkley

Cheers for now,
JohnB of NZ

17

The gas is nitric oxide. It only get produced if you use concentrated
nitric acid. This bites very fast and you should dilute it until only
colorless hydrogen gas is produced.

Tony Konrath

18 
The nitric we use at school started off at 70%

Thus far, I have bought mine from Rio. I cannot find anywhere that
says what the concentration is, as it comes in the bottle. Does
anybody know?

Noel

19 
Mustard gas was Chlorine...... however, the brown gas from Nitric
acid is just as toxic

Was going to just let the original comment pass as near enough, but
things spiral into strange places, sometimes. I don’t know if Ian
means mustard gas ~is~ chlorine or not - doesn’t matter a whole lot.
Mustard gas is a class of chlorine/sulfur/sometimes phosphorus
compounds. Chlorine, no, chlorinated, yes.

The brown gas from nitric acid is nitrogen dioxide. When you
dissolve it in water (as in your eyes, nose and lungs - or a beaker)
you get nitric acid. Don’t breathe or contact it, ever. It’s similar
but not identical to other acids - HF is hydrogen fluoride, a gas.
When you dissolve that in water you get what’s still called HF -
hydrofluoric acid. Then it will release HF, a gas, again under
various circumstances (heat…).

My brother was a tech with missiles, and he told me about how
sometimes the radio would crackle, “Hey, there’s a BFRC (big red
cloud) coming your way.” Which meant run as fast as you can. Used as
a oxidizer with rocket fuel, but not your typical chem lab acid,
either…

If you get a BFRC in your shop, drop everything and leave
~immediately~.

20

Hi Sharon,

I disagree about the formula being easier to deal with, though, but
that's because math is not my strong suit; I wouldn't be able to
translate my measurements into that formula at all. It's more
precise, certainly, but I find it's easier to just measure out 4
cups of water to 1 cup of nitric (with glass measuring cups,
natch).

The beauty of the formula (and the reason I keep harping on about
it), is that it’s a really useful formula for use with any sort of
dilution problem, ie mixing one strength of liquid to another
strength. It really is easy once you get it.

Perhaps one thing which I failed to communicate clearly, is that the
“Final Volume” in the formula, is the total volume of acid
(“Original Volume”) AND water added together, ie the diluted solution
volume. So:

Original Concentration X Original Volume = Final Concentration X
Final Volume

where:

Original Concentration refers to the strength of you acid as
purchased; Original Volume refers to the volume of acid used;

Final Concentration refers to the strength of the solution after the
water has been added;

Final Volume refers to the total volume of the acid AND water added
together (that’s why you need to subtract the “Original Volume” from
the “Final Volume” to calculate the amount of water needed).

The real value of using a formula like the above, is if you purchase
(or are given) really strong acid, and you want to dilute it to a
specific (and quite weak) concentration. Just saying mix four cups
of water to one of acid, will give a very different result for one
person starting with 70% or stronger acid, than it will for the
person using 38% or weaker acid. That’s why I asked people to state
their acid concentration, as such ratios are fine, and accurate
enough if your acid is in the same ballpark, concentration wise, and
you don’t like the maths of using a formula. So if you don’t like the
maths, and someone says “four cups of water to one acid” and they
state 70% strength, at least that way, if your acid is only 38% or
weaker, then you know you only need two cups of water to one cup
acid.

Helen
UK