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Silver Etching Help

Ok…all you troubleshooters. Can I have a little imput on this
etching question? I am etching fine silver for 4-5 hours in ferric
nitrate for a deep etch for champleve enameling. I am using PNP paper
as the resist. I am suspending the metal upside down while attatched
to a small boat of styrofoam. I check the piece every hour. I am
getting an incredible amount of blackish scum deposit on the metal
that has to be brushed off with a toothbrush. I am sure that this
also slows down the etching process. Any reasons or solutions? Any
ideas on the reason for this dark scum. I mix the crystals with
distilled water. I have also used a chemical stirrer to slightly
agitate the solution but the drawback of that method is there is a
slight wave pattern formed on the etched area and sometimes the
center of a large piece (4" x 6") will be etched a little deeper than
the edges. That is not very good for even layers of enamel. Any help
would be appreciated. Thanks in advance, Jan Harrell

I read quite some time ago on this forum that someone used an fish
tank air blower (I’m not sure what it is really called) in their
ferric nitrate solution to keep it agitating constantly during the
etching time. This apparently kept the scum from sticking to the
piece. I’ve never tried it myself, but it may be worth exploring.
–Vicki Embrey

Hi Jan; When I was an undergrad metals student, we used nitric acid
for etching silver. I had never heard of ferric chloride until I
started etching on copper plate. We also used a chemical called
"Dutch Mordant" which I believe was only ferric chloride. Someone
feel free to correct me if I’m wrong. When I was at one of Linda
Threadgill’s spray etching workshops, she used ferric chloride. I
think, if you’re going to be doing a lot of etching, the spray
etching technique is excellent, as you get very even bite and
virtually no undercutting. It’s not really that expensive to set up
for it. You can check out a set of slides on her system from
Society of North American Goldsmiths.
to get on joining SNAG if you’re not a member. SNAG has
some wonderful benifits. It’s a lot for the money, including a
subscription for Metalsmith magazine.

David L. Huffman

Just a note on using a cheap aquarium air pump to agitate chemicals
when etching: the pump goes OUTSIDE the solution, not in the solution.
Use a covered plastic container and sit the pump on top.


The fish tank pump was duct taped to the container holding the ferric
nitrate; the vibration keeps the ferric nitrate in solution, and
speeds up the etch. This from Karen Christians’ photoetching protocol,
which she shared with people on this list a year or two ago.


Vicki, The aquarium pump is taped on top of the etching container
providing constant agitation of the ferric nitrate. I use this method
for both ferric nitrate and ferric chloride. Etching in this manner
requires the image to be face down so the etched particulates can fall
to the bottom.


Jan, When I have etched with ferric nitrate, I do see a fine greyish
precipitate on the metal, but I just leave it alone and continue with
the etching.

A couple of questions.

  1. where did you get your ferric nitrate

  2. what is the concentration of the etching solution

  3. I first heat up the distilled water, but de-ionized water would be

  4. What is on the chemical stirrer (plastic coated)?

Try using an aquarium pump strapped to the top or bottom. This makes
for a more uniform vibration. Your etch could literally take a full
24 hours. Just leave everything alone. This is a slooowwww etch.
Your alternative is to use nitric acid which is just fine. I just
find that the ferric nitrate is just safer.


Jan, could your ferric nitrate crystals be old? It looks like you
have done everything right, including using distilled to mix the
mordant. We got ours from Bryant Labs and they are doing a good job
of etching, although it does take quite a bit longer on silver than
ferric chloride does on copper; we’ve never had any black gunk. This
week we also discovered that the PnP will hold up to the silver
mordant (clear, label says contains nitric) sold by Rio Grande…but
that mordant is slower than the crystal mix. As to the wave pattern,
we sometimes use a fish tank aereator to keep our mordant active but
have never had any extra patterns appear, although we have seen that
with overly strong ferric chloride on copper. What proportions are
you using for water to crystals? Another possibility might be to do
a deep etch with ferric chloride on 14 or 16 ga. copper with the PnP
image made negative and then use a rolling mill to transfer the deep
pattern to fine for champleve. Donna…(I sat next to you in the R.
Mawdsley workshop at the last Enamelist Conference in Ontario)

Whilst wandering lost on the web last night, I came across a link on
etching. It was a printmaker’s site. The article was discussing
etching with ferric chloride, and they addressed the issue of black
gunk. The solution the article offered to this problem was using a
vertical tank rather than a horizontal tank, and also using the
bubbling aquarium areator (sic). I’m not sure how you would go about
making a vertical tank- maybe use a file box? Good luck- Anne

***Hallo David, I am interested in the spray etching technique, just
searching for a good etching technique myself. The only problem is how
to get the Living in the Netherlands I am not very
anxious to become a member from an american society of goldsmiths, and
besides that I am using so many techniques I can’t become a member
from every society that has something to do with them. Many artist
don’t bother, but I like my work to be technically perfect, or just as
perfect as is possible and as perfect as it needs to be to be good
work. So please, is there a website were the technique is explained?
Or is there an article you could send me (in pdf maybe, so it is fast
to send?) I am very curious, also if you can use this technique with
all the different kind of etching fluids, for silver and copper? Hope
I don’s ask to much…want to use it to make a relief underneath my
transparent enamels. thanks, Marleen B.Berg.

    I read quite some time ago on this forum that someone used an
fish tank air blower (I'm not sure what it is really called) in
their ferric nitrate solution to keep it agitating constantly during
the etching time. 

G’day; pardon my jumping in, but having kept tropical fish over a
period of 40 years, and done a bit of etching too, I have a couple of
suggestions: 1) Use an air diffuser stone with the aerating pump
which will provide a better movement of fluid than having the bubbles
rise from a tube. 2) Don’t have the bubbles rising under the work as
some may become trapped and stop the etching fluid from doing it’s
job; Have the bubbles rising to one side of the job, and the fluid
will circulate nicely.

These little pumps are easily available from pet shops and you’ll be
amazed at the low cost - probably less than US $10. I bought one a
couple of weeks ago to blow dust away from a jewellers saw; it cost
NZ $12 and is quite adequate. (US dollars have over double the value
compared with ours) Cheers, –

John Burgess; @John_Burgess2 of Mapua Nelson NZ

    I am getting an incredible amount of blackish scum deposit on
the metal that has to be brushed off with a toothbrush. 

Blackish scum suggests to me a chemical contamination, a reaction
with the iron. Is it possible you’re getting any kind of ammonia in
the solution? Ammonia causes this reaction. I suppose it would
possible with other chemicals accidentally introduced to cause a
similar reaction. Are you using a glass or plastic container to etch
in? I wonder if some of your set up materials might be having a
chemical interaction with your solution? I wonder if ascetic acid as
by-product of tape adhesive or butyl latex caulk might cause this.

The wave pattern (or ripples), from experience, is generally caused
from too strong a solution. When etching large open areas, you need to
cut your solution by about 15%-20% more water. Your etch will be
slower, but more uniform, with less undercutting. If the etch is going
too slow, you can either try the spray or rocker method.

Also, when using an aquarium bubbler, remove the airstone (most
decompose and react with the solution), and protect the piece by
placing the end of the hose under a glass sheet, and then suspend your
piece above the glass sheet. This allows the solution to be agitated,
but you won’t get scour marks from the increased action directly
against your plate. Actually, I pierce the hose with a large needle
down the length of the last 8", and plug up the end. This allows a
pretty uniform agitation and oxygenation, without a large
concentration in any one area. Oxygen combined with the ferric,
increases the etching action. Therefore, when you have a large
concentration of air, such as at the end of a bubbler, the solution
has a tendency to etch more rapidly on the end of the plate closest to
the air, causing scour marks, which look like pits or striations.

I hope this helps to solve your problem.

depening on size of work, a largemouth gollon jug should do a fine
job Leon K in hot sunny MO

Marleen: I’m sure you’ll get several replies…the spray etching
technique was developed or patented by Linda Threadgill who is a
professor at a university in the state of Indiana (sorry I cannot
remember which one). You can locate her on the web:

I got to attend her workshop here in Maryland and it was wonderful.
I think she does workshops in Europe too. Good luck!

–Sherry Terao

For relatvely simple etching equipment ideas, look at the printed
circuit board industry. Here is where almost all chemical etching
is done- more every day than in a year of art etching. Here are a
couple sites that show bubble etching and spray systems:

These are a litle more than home made, but inovative souls should
get some help in building something. Yhere is more ouy here in the
printd circuit world.


To add a few more sites on etching:

The two chapters at rickadee net show some equipment examples and