Mordant for etching gold

Jewelry Discussion
1

I just gave a workshop in etching copper with Ferric Chloride, using
PnP. Several of the participants work in gold and silver, and now
that they are familiar with the process are planning to etch their
silver with Ferric Nitrate.

However,one plans to work on gold. Her question is will Ferric
Nitrate etch Gold? She usually works with 18 K. some 14 K. She wants
to use the PnP, which rules out Nitric Acid, as the PnP will not hold
up in it…

I have searched the archives, but have not found any references to
etching Gold with Ferric Nitrate.

Alma Rands

2

Gold is almost impervious to all acids and acid salts, it takes a
concentrated mixture of nitric and hydrochloric acids (Aqua Regia)
to etch it so your student is out of luck with regards to using PnP
Blue.

James Binnion
@James_Binnion
James Binnion Metal Arts

360-756-6550

3

Hi, very few things will etch gold, pur gold will only dissolve in
aqua regia but you can etch lower carat gold with nitric acid as it
will etch the alloy grains leaving the gold behind. The depth of
etch will be very shallow as the grain size of the gold will only be
a few microns and the etching may be almost invisible to the naked
eye. You will have problems with high Ni content gold alloys though.

Nick

4 
very few things will etch gold, pur gold will only dissolve in aqua
regia but you can etch lower carat gold with nitric acid as it will
etch the alloy grains leaving the gold behind. The depth of > etch
will be very shallow as the grain size of the gold will only be a
few microns and the etching may be almost invisible to the naked
eye.

This will not work with high karat colored golds and might work with
14k but more likely with 10k or 9k. Depending on how the gold is
processed you might see a grain boundary attack, cast material will
more likely show some grain boundary etching but wrought sheet will
not show much if any at the grains with just nitric. In any event
the material would need to be polished in such a way as to remove the
surface smearing of thpical polishing to expose the grains in such a
way as to be available for the etching. This type of etching may be
suitable for making micro-graphs in a lab but will be imperceptible
to the naked eye.

James Binnion
@James_Binnion
James Binnion Metal Arts

360-756-6550

5

Potassium iodide/iodine will etch gold but it is much slower than
aqua regia.

A very concise two-page document can be found here.
http://www.microchemicals.eu/technical_gold_etching.pdf

Jeff

6 
A very concise two-page document can be found here.
http://www.microchemicals.eu/technical_gold_etching.pdf

The same company sells a HF/HNO3 prepared etchant for gold:
http://www.microchemicals.eu/etching_mixtures.html

Al Balmer
Sun City, AZ

7

Aqua regia is childs play compared to any mix with HF. I’ve used
many nasty chemicals over the years, all deserve respect and
precautions but HF is best avoided.

Jeff
Demand Designs
Analog/Digital Modelling & Goldsmithing

8 
Aqua regia is childs play compared to any mix with HF.

Thanks, Jeff. I saw this post yesterday and a cringe went up my back,
but I just passed it by. Then I though,“You know somebody needs to do
something about that!” I know nothing serious about gold etching,
though I was thinking maybe some fluorine mix might do it. (HF alone
will not), and I’m unfamiliar with a HF/HNO3 mixture, but I do know
enough to know what it means. The danger here is that some reader
will say, “Oh, I always wanted to etch gold, I’ll get some and try
it.” There are chemicals that are relatively benign - flux is one of
those, there are chemicals that are fairly hazardous, like strong
mineral acids, and there are chemicals like pure hydrazine that are
considered too dangerous for anyone but a bona-fide, certified lab to
posess. An HF/HNO3 mix would at least approach the third category.
I’d say that thinking of it as “liquid death” and treating it
accordingly would be appropriate - by no means excessive. If I were
in your garden variety shop and you had some and cracked the lid, I
would leave the room immediately, and not come back. Once you put
metal in it, which will generate gas, then it’s all over. Certified
fume hoods, oxygenated acid proof full face masks, HazMat suits, even
remote manipulation - all that would be reasonable in this case. In
any case, getting a tupperware container and pouring some in and
putting a piece of gold into it could be tragically foolish, in
minutes.

9 
Aqua regia is childs play compared to any mix with HF. I've used
many nasty chemicals over the years, all deserve respect and
precautions but HF is best avoided.

So is aqua regia. Both are dangerous, in somewhat different ways, but
both can be used safely. Anything that can etch gold is dangerous
and must be handled with the utmost care.

Al Balmer
Sun City, AZ

10

I want to thank everyone who responded to my query about etching
gold. I will pass the along to my student. All in all, I
think that once she is aware of the difficulties and dangers she will
abandon the whole idea of etching gold. Neither of us have a death
wish.

Alma

11 
I saw this post yesterday and a cringe went up my back, but I just
passed it by. Then I though,"You know somebody needs to do something
about that!"

I second that also. I meant to reply but for some reason forgot.

If you look at the halides on the periodic table, from the top to
the bottom you have Fluorine, Chlorine, Bromine, Iodine, Astatine. In
terms of reactivity, Fluorine at the top is the MOST reactive (read
into that also MOST dangerous) and Astatine at the bottom is the
least reactive, with the ones in between following the trend. All the
halides will form acids with hydrogen and hydrochloric acid (HCl) is
bad enough and serious consideration must be given to safety
precautions when handling it. Hydrofluoric acid (HF) is a no no as
John says to all but qualified and certified lab professionals.
Nitric acid (HNO3) is also very nasty and great care must be given
with regards to safety procedures when using it or when using Aqua
Regia (combination of HCl and HNO3).

If you combine hydrofloric acid and nitric acid (HF/HNO3) in a way
similar to aqua regia and use it in a jewellery workshop or studio
and you are asking for SERIOUS TROUBLE. DON’T DO IT!!!

Helen
UK

12

Perhaps some of you missed There is way to etch Gold with hydrazine -
I Have used this process when needed (rarely) over years and years
since My printmaking days in an MFA programme.

however hydrazine should never be opened, possesed, or worse, used
in a small scale jewelers studio _ unless you have a full blown
laboratory that is licensed in your back yard.

if i were in the poster’s town i would be errant not to report that
the person is risking the lives of everyone in his studio and within
100 ( immediate and more with a strong wind) yards of the gases
generated when adding metal to it!

it must be licensed for use. and dispoed of very specifically…

do not try obtainng it or using it :the reultant gas kills with the
swiftness of zyklon b…and death is horrible painful and prolonged
and will occur if you decide to try this.period!!!

of all the posts that get snipped by the moderator(s) any that
recommend or suggest hydrazine as a viable alternative to the safe
and tried and tested process i have provided below is simply mind
boggling.

To etch gold one has to use a traditional photo process:

Clean your metal in acetone, MEK (methyl Ethyl Ketone) or lacquer
thinner In a darkroom working under a yellow lamp ( not red), Prop
your metal Plate up against the container wall( glass or stainles
only),apply Kodak brand KPR resist to plate by brushing it on or
dipping it ( if Its a small piece)

Let it dry in the dark for two days ( about 48 hours at any rate)
Contact print film sheet under a pane of glass and expose it to
Sunlight, a high powered sodium halide light, sun lamp, or bank of
4, #1floodlights- even a head of 24 led’s will do the job! If you are
lucky enough to have access to an arc lamp 5 minutes is Required for
Perfect results, in sunlight, figure you will need intense sun at
About 4 hours exposure ( say between 11 am and 3pm EST)

Develop the plate of metal in KOP ( a kodak product) for 3-4 minutes
Lightly agitating it as for film development( the solution is washed
Over the metal by lifting an edge of the container ( a 2 1/2" sided
Steam table pan of stainless steel or glass pyrex type baking dish
Works great!) And lowering it repeatedly for the specified amount of
Time ( you can go too long in which case your material will begin to
Lose the detail you intended as the resist breaks down)- do not use
plastic for the kop solution it will eat it rapidly

Wash the metal under running warm water and the image will appear. (
i Usually put a generous amount of sodium bicarbonate in the washout
Sink ( about a quarter of an inch thick ) to neutralize the solution
Before it goes into the grey water that i use for gardening, etc-
you May want to do the same before it hits the city sewage system- it
is Very corrosive stuff and not healthy for any water system
untreated)

Etch the image in a solution of 1 part nitric acid, and 3 parts
Hydrochloric acid. The photo image will appear immediately when
etched In this mordant.

It is usefull to have a large turkey, crow, raven or other feather
on Hand to brush away any bubbles that seem to cling longer than
necesary From the areas that have no resist on them.

Use any of the solvents mentoned above to remove the reisit when you
Have achieved the desired depth of etch, then wash well and finalize
With a neutralizing rinse of about a pint of water to 3-4
tablespoons Of sodium bicarbonate ( more is actually better in this
case, but a Paste is overkill!)…

If you have questions feel free to email me off list Dr.R,E,Rourke

13

Orchid is a metals thread, by and large. When I say to solder
something, I don’t feel the need to say, “Don’t point the torch at
your hand, don’t drink your pickle.” and the like, because that is
assumed. Chemistry, as in professional chemistry, is no different.
If you go anywhere online and research “Uranium Hexafluoride” you’ll
find the process layed out: Get uranium cake, treat with HNO3, treat
with fluorine, etc. Pretty simple, except for getting the uranium to
begin with. What they don’t tell you, because it’s assumed, is that
this all occurs in a $25mill facility in the absence of human
beings, because your survival time upon entering the room would be
20 seconds, max. The point of all this is that you need to use your
brain. First off, don’t post suicidal processes online to begin with
(bozo), and if you should read such things, think about
self-preservation first: “Wait a minute - maybe there’s a reason the
chemical supply house won’t sell me that?” The chemistry of jewelry
is fairly benign most of the time - flux, Sparex, ferric chloride,
some fairly hazardous plating solutions. But when you get into
photoetching, gold etching, plastics and other, more arcane things
you can easily kill yourself if you don’t educate yourself first.
There are some here on Orchid who consider flux and Sparex to be
some hazardous, toxic stuff - well all chemicals deserve respect,
but borax is in laundry detergent, fercrissake. It’s far better to
have that than to have people washing their windows with HF, though.
A little fear is better than foolishness, most of the time. Today
R.E. mentioned etching with hydrazine, with appropriate GIANT RED
FLAGS. 99% of the readers here are better off not ever being withing
100 yards of the stuff, and the other 1% knows just what to do with
it. Understand that there are chemical things that you may become
aware of that carry a great weight behind them, though what you read
might just say, “Do this, Mix that” and if you don’t understand that
it could be very, very bad indeed.

http://www.donivanandmaggiora.com