Fifty years ago I watched my Dad etch sterling (925) and coin ((90%)
silver using Nitric Acid that he bought at the local drug store. He
made an example of what this acid would do to me if I should ever get
into it by dissolving a silver dime in it. Now that I have retired I
have decided to try my hand at etching silver items. I bought a
bottle of 96.9 pure Nitric Acid but it will not dissolved silver. So
I bought a bottle of 99.5 white fuming nitric acid hoping this
wrought do the job, it only turns silver coins black. What type of
nitric acid would dissolve a silver coin and where can I find it,
Your acid my be too strong to give an ionic reaction, I use a 25%
nitric solution. Add 1 part acid to 3 parts water {do it that way
round otherwise the reaction will boil the acid and probably burn
your house down} This will allow the etching of silver in a fairly
controlled manner but at a reasonable rate.
I have no idea what kind of Nitric Acid a drug store would be
selling. I got mine from a chemical Supply house. I got the regular
Nitric Acid, not the purest form as it is cheaper. That stuff really
worked. However, since I have switched to using the photo etching
process with PNP, I use Ferric Nitrate for my etching,on silver, and
ferric Chloride on copper and no longer use Nitric Acid.
I bought a bottle of 96.9 pure Nitric Acid but it will not
dissolved silver. So I bought a bottle of 99.5 white fuming nitric
acid hoping this wrought do the job, it only turns silver coins
black. What type of nitric acid would dissolve a silver coin and
where can I find it,
You’ve got the right acid. But don’t use it so concentrated. It needs
to be diluted to work well. Usually, somewhere in the area of 10 or
15 percent acid to water should do the trick. Remember, when
diluting, to add the acid to water, not the other way around. Water
added to concentrated acid can almost explosively boil, spattering
you with hot acid. Nasty. Adding the concentrated acid to a greater
volume of water, slowly, prevents this from happening. The dilute
acid is also a good deal safer to work with. Be really careful with
the concentrated acids, especially the fuming one. Use good
ventillation when handling it.
OK, this is nitpicking, but… my first time getting nitric acid on
me made a huge impression, so I’m going to share.
Your fingers will not turn yellow (though fingernails will, or brown
anyway).
On the occasion in question, I noticed a white spot on my hand,
thought “Huh! Maybe I got acid on me.” But it didn’t feel like
anything… Later that evening, the spot (about an inch by a half
inch) was blue. Not blue-ish, honest-to-God blue, the color my TV
screen turns when there’s no reception. This got my attention. But
still didn’t feel like anything.
The next morning, my spot was black. Not black-ish… and I’m
thinking “holy s___, what next?”
OK, well, after that it’s an anti-climax. Over the next few days,
the black skin flaked off, never hurt, the affected skin was not deep
enough to leave a mark or anything, but you know, that really just
can’t be a good idea.
A student where I teach, back when I was a student there, put on
gloves and decided that that meant she could just reach into the acid
to take out her piece. Turned out three of the glove fingers had
holes in them.
96.9 pure Nitric Acid but it will not dissolved silver. So I bought
a bottle of 99.5 white fuming nitric acid
YEEEEOOOOW Larry! That’s rocket fuel… You need more like a 10%
solution, maybe 15% - etchers here could pin that down, I’m sure.
And your 99.5 (either one, actually) is prone to explosion if it’s
even introduced to water casually. Either exchange them or put on
your hazmat suit and dilute it with the greatest care (Acid into
Water, constant stirring, verrrrrrrrry slowly). DO NOT do that
without personal protection - lots of it.
Nitric acid in particular behaves differently when it’s pure or
nearly so than it does when diluted with water - others do, too, but
nitric in particular. There’s a few reasons, the main one being that
in order to ionize it needs water- Helen the chemist probably knows
the story better. But dilute nitric is entirely different from
concentrated in many ways.
If you just plopped the silver in a dish on your bench, you’re lucky
it didn’t work because it would have gassed you and more in
seconds…
The next morning, my spot was black. Not black-ish... and I'm
thinking "holy s___, what next?"
What you experienced is a silver nitrate burn. Silver nitrate is
formed when you dissolve silver in nitric acid. Silver nitrate is
photo-reactive as are many other silver compounds. Once you exposed
it to light it began to turn, first blue then purple then black.
Photo- reactive silver compounds are the basis of film photography.
Helen the chemist probably knows the story better. But dilute
nitric is entirely different from concentrated in many ways.
Is it possible that what Larry experienced when he observed the black
layer with fuming nitric acid, was passivation? With some metals, the
conc nitric will form a protective oxide layer which prevents further
corrosion/etching. Used dilute it should etch nicely - but it’s still
horrible stuff!
I began my artistic life as a printmaker, and was taught to only use
nitric with heavy gloves designed for that; with the proper
respirator mask rated for nitric; with a heavy duty rubber apron;
closed shoes; really excellent ventilation.
As I prepare to go back to using nitric, but this time with silver,
I’ll be following all of those precautions! Supplies can be
purchased from Graphic Chemical & Ink, and printmaking supplier that
I have used for many years.
Please be sure to have fast access to running water, and immediately
rinse any that you get on you, or on your clothes or the floor.
Nitric is a STRONG acid and WILL eat most things fairly quickly!
What you experienced is a silver nitrate burn. Silver nitrate is
formed when you dissolve silver in nitric acid. Silver nitrate is
photo-reactive as are many other silver compounds. Once you
exposed it to light it began to turn, first blue then purple then
black. Photo- reactive silver compounds are the basis of film
photography.
Makes sense. So you’re saying it wouldn’t have gone this way if the
acid had not been fairly used already? What happens if there’s no
silver dissolved in the nitric?
I have a very interesting splash burn mark on my right cheek, right
on the edge of my safety glasses. As I was carrying nitric to the
disposal in chemlab the very large beaker (about 2 liters) decided
to do the equivilent of a mass wasting, and split in two pieces and I
splashed acid all over the place. my next action was to walk to the
shower and pull the ring. this attracted the lab assistant who came
over walking through the smoking floor to me and asked me if I
needed anything.
and the moral is: as beth says above – wear all the safety equipment
that you can put on. I ended up with a small drop shaped burn scar on
my cheek. real lucky.
So you're saying it wouldn't have gone this way if the acid had not
been fairly used already? What happens if there's no silver
dissolved in the nitric?
Correct, if there was no silver dissolved in it then you would end
up with the yellow burns from the nitric itself. You had the yellow
burn as well but could not see it due to the coloration from the
silver nitrate.
This formula’s answer to all the artist who have inquired about
working with Nitric Acid. It is a process that has proven to make a
perfect etch with all non-ferris metals. Stainless Steel, Aluminum,
and Titanium require other acid-chemical mordants,
This formula's answer to all the artist who have inquired about
working with Nitric Acid. It is a process that has proven to make
a perfect etch with all non-ferris metals. Stainless Steel,
Aluminum, and Titanium require other acid-chemical mordants
I have been etching sterling for several years now and bought a
gallon of Nitric which was reagent grade or 70%. I haven’t used it
for about three years and it is still in the original glass
container. Does it keep it’s strength over time or will it get
weaker? I have several students and was planning to do an etching
class but need this info before starting.
i believe it concentrates due to evaporation with time. I have some
that was in a glass (old vinegar type) jug, with a non-metallic lid (
you can buy lids with chemical proof seals at Berlin packaging.com,
as well as just the seals, and a bevvy of various nalgene and kimex
bottles, wide-mouth containers etc for safe chemical storage, as well
as packaging for your work, storage for home and shop etc.- they have
some unique things in their whopping catalogue) that i just used last
weekend on some fine silver and gold sheet- worked really fast, in
fact, faster than I remember when it was first opened. In Harold
O’Connor’s book he gives formulations for various metal etchants
using either nitric acid chrystals, ferric nitrate or ferric sodium
crystals depending on the metal (in addition to a number of other
formulas, colourants, etc. for ferrous and non-ferrous metals and
some for reactive metals as well- though electrical current is
necessary for the reactive group, tantalum and some platinum alloys,
in addition to mordants that must beused for some applications)- I
highly recommend the book,The Jeweler’s Bench Reference, it is
invaluable and have a few copies for sale if anyone is
interested-$24.00 postpaid in the US- by destination via USPS global
express for non-contiguous US destinations…not that this was a sale
ploy- just a hard to find, i think, title that i think is out of
print- that i bought a bunch of for students and have some
extras…let me know OFF LIST PLEASE if you want more info on the book
or its contents…I really have to get my site working!!! rer
Nitric in a capped, glass jar will keep it’s strength for a long
time. I had a 200 ml plastic bottle of it for 20 years (from when I
taught chemistry) and it still had a punch when I broke through the
plastic by accident - just glad it was not concentrated sulfuric, I
could live with the yellow stains from the nitric.