Etching Options for Champleve
by Coral Shaffer
from Volume 17, Number 4, October 1998
I have found through my research on metal etching that there is a
plethora of information out there. I hope by compiling it
and offering it to you, you will be better able to choose the best
option for your champleve needs. There are of course means
other than etching to prepare a surface for champleve enameling,
namely piercing and soldering, forming with a hydraulic press,
stamping or engraving. This article however will deal only
with the etching options. And only with those materials
suited to relief etching (where the resist is applied along the
design lines and these lines remain raised after etching) rather
than intaglio etching (where the entire surface is covered with
resist and the design lines are scratched away and subsequently
eaten away by the etching process).
In order to etch the design of your
choice, you must first somehow transfer that design, in the form
of a resist, to your metal. The following are all etchant
resistant (to some extent) and will adhere to the metal.
1. Graphing tape, hole reinforcements, Contact paper, dots
and labels, vinyl letters (stick-backed things you find at a
stationery store) will all work quite well as a resist if the
mordant isn't violently strong and you do not need to etch too
deeply. If you apply these to clean metal and burnish them
down, they will hold better. Contact paper or its equivalent
can be burnished in a solid sheet and then areas can be cut away
with an Exacto knife where you wish the metal to be bitten.
With the exception of the contact paper, these stick on shapes are
fast and easy to apply. The limitation is that your design
must pretty much consist of straight lines and circles.
Scotch makes a blue masking tape called Long-Mask TM that works
very well for the back of the pieces.
2. Lacquer-based spray paint (e.g. Krylon Interior/Exterior
paint) will also work as a resist. You can spray it through
a stencil of your own making; a commercial stencil available at
craft supply stores; or through or around a found object such as a
leaf, a doily or some lace. Make sure the stencil is firmly
in place, then spray it and let it dry. Repeat this for
better coverage and resistance. Spray paint also works very
well for the back of the piece where you just need to protect the
metal and not transfer a design. Fingernail polish is also serviceable
for protecting the backs and edges. Graphic Chemical and Ink
Co. (see list of suppliers) sells a nontoxic resist for the same
purpose called Z*Acryl that can be removed with household ammonia.
3. Lacquer and paint pens are easy to draw with and some
hold up quite well through the etching process. I have had
limited success with Sharpie pens, but they are OK for a quick,
shallow etch. Sharpie makes an 'industrial' pen that
protects longer than the ones found in stationery stores.
The very best pens, in my opinion, are what I call 'paint
pens'. The ones I use are Speedball pens called 'Painters' -
opaque paint markers that come in two different point sizes.
If the lines are wide enough, e.g. 1/32" for a 1/32"
etch, it will hold up for the entire etching process.
4. Asphaltum, a dirty word to some of us, is the classic
acid resist for relief etching. It is messy and takes a long
time to dry - but it remains a good option in some circumstances,
such as the need to etch a 3-D piece or for silk screening a
production run. Mixing liquid asphaltum with beeswax and
rosin makes it less brittle and better able to adhere to the metal1.
It can be painted onto clean metal with paint brushes or squeegeed
through a photo silk screen. I find that a few seconds in a
300 degree F kiln or under a heat lamp will close up the pinholes,
speed up drying and make it less sticky to work with. Make
sure you watch your piece closely or you will soon have a black
puddle with no recognizable design left! Rio Grande sells a
nifty set up called the Rio Master Etch-PressTM
System that allows you to 'burn' your silk screen and print
through it all on the same unit. The print size is
3-9/16" x 5-9/16". Rio Grande also sells another
liquid resist (Rio Etch Resist) for silk screening which is not
asphaltum, but which, I understand, works quite well, especially
if it is heated in a 200 degree F oven for 10 minutes to set it
5. And now we come to my 'fave', PnP Blue. This is a
toner transfer sheet used by amateur circuit board printers and
works extremely well for champleve etching. It is very
simple to use - all you need to do is draw your design and
technology does the rest! Because it is clean and requires
no drying time, it is particularly suited to class
situations. PnP Blue is a resist bonded to a sheet of
polyester. You transfer your design to the PnP with a copy
machine or a laser printer. What could be simpler? The
PnP toner design is then ironed onto your metal with a household
toner acts as the 'glue' attaching the resist design to the
metal. The back and edges should be covered with some other
resist. The limitations of this method are that only flat
pieces of metal can be used, and it is time consuming for large
runs. There is another toner transfer material on the market
manufactured by DynaArt, but I have found it much more difficult
to work with. You might wish to investigate it
yourself. If your needs are for high volume production, you
may wish to look into pre-sensitized copper available from Kepro
Circuit Systems Inc. and other suppliers. Basically, this is
copper pre-coated with a material that will accept your art work
through a photo developing procedure. Materials are also
available for sensitizing the metal yourself. I find it hard
to want to bother , when PnP Blue is so much simpler and needs no
Now that your etching resist is duly
attached to your metal, it is time to actually etch it. For
this you will need a mordant, also known as an etchant - the liquid
that eats away the unwanted metal parts in your design. The
metal you are etching and the characteristics of the etch you want
will determine the type of mordant you will choose. I was
hoping I would find a 'magic bullet' etchant, one that was
non-toxic, fast and easy to dispose of. I read all the
material I could find about mordants used commercially and, alas,
there was no magic bullet. Some of the commercial etchants
for copper or silver I felt were too dangerous in a studio setting
so I didn't even try them: sulfuric acid mixed with 50%
hydrogen peroxide; chromic acid mixed with sulfuric acid; ethylene
glycol; and alkaline cyanide mixed with hydrogen peroxide.
Following are the mordants I did try:
1. Nitric Acid. Nitric acid, diluted with two
parts water to one part nitric3,
will quickly etch both copper and silver. The problem is, it
is potentially quite toxic to you and wreaks havoc on your
resist. You need to supervise this etch constantly and brush
away the bubbles that form so that they won't block the etching
action. Because of the violent action of nitric, the etched
lines are often jagged. Use this acid with all the safety
equipment you can: rubber gloves, apron, goggles, and heavy
duty ventilation. Keep some baking soda handy to neutralize
spills. Used nitric acid is a hazardous waste - consult with
your local waste authority about proper disposal.
2. Ferric Chloride. This is the mordant I am
most familiar with. Though it is messy, it is much less
toxic than nitric acid and gives a nice, even, albeit slower,
etch. It will work on copper or brass, but not on
silver. (See Ferric Nitrate listed below for a similar
etchant for silver.) I find that a slightly diluted FeCl3
solution works as well as, or better than, the full strength
stuff. Three cups of 42 degree F Baume Ferric Chloride mixed
with one cup of water is recommended. As ferric chloride
etches, it can leave a layer of sediment on the exposed copper,
which acts as a barrier to further etching. To counteract
this, I etch my pieces upside down - stuck to a piece of styrofoam
with carpet tape. The whole kit and caboodle can be removed
from the bath to rinse it off, which you should do often, and then
returned to float in the vat of ferric chloride. The etching
rate can be enhanced in three ways: by agitation, aeration,
and heat. One of the simplest ways to achieve the first two
is to use an aquarium pump and 'bubble wands'. The latter
are a type of air stone for fish tanks that look like thin tubes
of turquoise styrofoam. (Air stones made from glass
particles work for a while, but then the glue that holds them
together breaks down and they crumble.) Attach the bubble
wands to the bottom of your container with electrical tape so that
the bubbles pretty uniformly cover the entire area. I have
used a homemade spray etching machine, which definitely speeds up
etching time, but I have not been able to control the etch
sufficiently - parts of the piece etch all the way through before
others are etched enough! Depending on the shape and
material of your container, heat can be applied with fish tank
heaters, a heating pad, a hot plate, a heat lamp, or even a Luxo
type lamp. Watch the temperature very closely. You
don't want to go over 175 degrees F, or your PnP resist will fail
to resist and asphaltum will be long gone. Heating will cut
your etching time almost in half, but be forewarned that it also
produces harmful fumes and weakens your resist. Proper
ventilation is important, and mandatory if you are heating this
solution. Protective clothing is a very good idea.
Spilled ferric chloride may not kill you, but it will ruin your
turn your skin orange. If the solution shows signs of
slowing down, it is possible to 'pump it up' a bit by adding
small amounts of hydrochloric acid and/or ferric chloride
crystals. After etching, it is necessary to remove the
ferric chloride residue before it dries onto your piece. If
it dries on, not even dynamite will get it off! Soak it in
household ammonia or a very mild hydrochloric pickle. Spent
ferric chloride needs to be treated as a hazardous waste.
3. Ferric Nitrate. When ferric nitrate crystals
are mixed 55% by weight in water, the solution works on silver
very much like ferric chloride works on copper; slowly and
evenly. I used the same bubble and floating technique and
was happy with the results. Ferric nitrate is classified as
'mildly toxic', but it is always wise to ventilate and wear
protective clothing. Investigate proper disposal.
4. Sodium Persulfate. This mordant is often
used by etchers of circuit boards. It comes in crystal form,
and needs to be mixed with water 24 hours before using.
After mixing, it has a short usable life - about two weeks.
The advantage of this mordant is that it remains clear (this
becomes most important when you drop your piece to the bottom of
the etching vat!) and does not stain your clothing. The etch
rate is comparable to that of ferric chloride and it has the same
hazard rating. However, sodium persulfate has only about 1/2
the copper holding capacity of ferric chloride, and so it will
take twice as much of the former to etch the same amount of
copper. It works better heated to around 100 - 110 degrees
F. Use the same health and safety precautions you would with
ferric chloride. Investigate proper disposal.
5. Ammonium Hydroxide. This mordant needs to be
heated to 120 - 130 degrees F and agitated. This results in
ammonia fumes that need to be carefully ventilated. After
seven hours in this bath, there was no visible etching action on
my copper test. Apparently, there needs to be some
ingredients added that I do not know about. I don't feel
this is a worthwhile etchant for the studio.
6. Cupric Chloride. The cupric chloride and
water solution needs the addition of hydrochloric acid to maintain
steady etch rates. When heated to 125 degrees F and 'bubbleated',
the etch rate is faster than ferric chloride, but, probably due to
the heat, the resist is more aggressively attacked and design
lines more easily etched away. I was anxious to try this
etchant because I read that it can be regenerated, making disposal
and buying of new material unnecessary. For small amounts,
cupric chloride regeneration begins by passing air through the
used solution until the color changes back to a bright emerald
green. This can be done with the same fish tank setup used
for the etching process. In addition, the density of the
solution must be checked with a hydrometer and periodically adjusted
by adding water. Also, the hydrochloric acid level needs to
be kept constant and to test that, a titration setup is
necessary. If you do a lot of etching and have the time and
ability to perform fairly simple scientific procedures, this
etchant could prove worth investigating.
7. Electro-etching Solutions. I have great
hopes for this etching option. It is basically the reverse
of plating - you are removing metal rather than adding metal to
your piece. The process is the same: you need a source
of DC power, an anode and a cathode and an electrolytic solution
for the electricity to pass through. The particulars,
however, are different. That is, you use different voltages,
temperatures and electrolytes - and it is very hard to find any
written information about it! I tried the following
electrolytes: salt water, Sparex, a dilute sulfuric (one
part sulfuric to twenty parts water) for copper and dilute nitric
for silver (one part nitric to twenty parts water). I have
not tried it but I heard tell that gold chloride is the
electrolyte of choice for etching gold. As this process is
the reverse of plating, your piece is the anode rather than the
cathode, and the cathode can be either a piece of the same metal,
or stainless steel. I had hoped, particularly in the case of
silver, that the metal removed from the piece would plate nicely
on the silver cathode, so that reclaiming it would be a
cinch. No such luck; it seems to just float around in the
electrolyte. But the
real beauty of this technique is that the resist lines are not
undercut! I have never seen such a straight sided etch with
any other etching process - even with commercially sprayed ferric
chloride. This means that even very thin lines will not disappear
as you etch. I guess the major drawbacks to electro-etching
are that it is not easy to do multiple pieces at one time and that
you need to have some extra equipment, namely a source of DC
power: dry cell batteries, a car battery, a transformer or a
rectifier, and an electrical connection to your piece. I
used a plating rectifier set at 1.5 volts and my pieces were done
in 2-3 hours. At this point, I only know of two ways to
attach the pieces to the DC power source. If you don't want
to waste any metal, then you would cut your piece to the exact
size of your design and soft solder a copper wire to the back
(before applying any resist there) and attach an alligator clip to
the wire outside of the solution. The back side of the piece
and lower part of the wire that will be in the electrolyte need to
be painted with a resist or they will etch away. If you
don't mind wasting some metal, you can leave a tab at one end of
the piece that will remain bare of resist and be attached to the
power source with an alligator clip outside of the solution.
(See illustrations.) Obviously, if the alligator clips were
in the solution, they would not last very long. It seems
wise to pickle and glass brush the metal after soldering to clean
off any oxides (PnP will hold up under this abuse, but don't try
this with asphaltum). The jury is still out on whether the
electrolyte should be heated and/or agitated. I know this is
important for plating, and so is probably also important for
electro-etching. However, my experiments were done at room
temperature, some with, and some without an air stone. I am
impressed enough with electro-etching that I intend to continue my
research and perhaps will write another article for Glass on Metal
with more particulars.
Table showing crude and
subjective comparisons between the different
etchants. 1 = 'good', i.e. least expensive, least
toxic, fastest working. 7 = 'bad', i.e. most
expensive, most toxic, slowest working.
CONCLUSIONS & GENERAL
If you should ask me my advice after
considering all this information, I would suggest that if you were
doing single pieces, you use PnP Blue for a resist, touch up with
paint pens, and electro-etch your pieces. If you don't have
electro-etch equipment, use ferric chloride (or ferric nitrate)
with or without the fish tank setup. I prefer using bubbles
but no heat, it is slower but safer, and less likely to
over-etch. If the air temperature is cold, a heating pad is
a gentle source of heat. Regardless of the etching setup you
choose, you need to check your piece often and rinse it off under
running water. Brush off any sediment with a soft paint
brush. This will speed up the etching process and allow you
to remove your work before it has etched too much. Whatever
chemicals you use, you need to have and read the Material Safety
Data Sheet first. It will explain the dangers in using and
storing the material and list safety precautions and emergency
measures. If you are doing big production runs, you might
want to investigate pre-sensitized metal and/or photo image
transferring methods (see suppliers list). Using cupric
chloride and regenerating it would save money and be kinder on the
environment for large volume etchers. It might be the case
however, that you would be better off finding a commercial etcher
for big production runs on copper. You can find them listed
in the yellow pages under 'photo etching', 'chemical milling',
'metal etching', or 'photochemical etching'. This is what I
have done for my production line of champleve. Chemical
millers use a sophisticated process to laminate a photo sensitive
film onto the copper, then expose and develop the film with your
designs and run it through a spray etcher. It is fast and
keeps the mess out of your studio. For further information,
please read through the footnotes, supply sources and bibliography
1. A recipe for
asphaltum 'plus': six parts by volume of liquid asphaltum to
three parts melted beeswax to one part melted rosin. Melt
the beeswax and rosin in a double boiler. Mix all
ingredients together and thin with turpentine and rubbing alcohol.
Specific directions usually come with PnP. See also Glass on
Metal, August 1996, pp. 60+.
I am sure you will remember to 'add acid to water, just like you
oughter'. DO NOT ADD WATER TO ACID.
Oxalic acid found at drugstores is the only thing I know of that
will remove ferric chloride stains from clothes.
Acu-Line Corp., 462 N. 35th,
Seattle, WA 98103, (206) 634-1618. Chemical machining
Bovano of Cheshire, 830 S. Main
St., Cheshire, CT 06410, (203) 272-3208 or 800
847-3192. Chemical milling of copper. $150-$250 for
first run, subsequent runs less expensive.
DyanArt Designs, 4707 140th Ave.
N., Ste. 212, Clearwater, FL 33762, (813) 524-1500.
TTS transfer paper (an alternate to PnP), wave action etching
machine, sodium persulfate.
Enamelwork Supply Co., 1022 NE
68th St., Seattle, WA 98115, (206) 525-9271 or 800
596-3257. PnP Blue with detailed instructions.
David H. Fell & Co., Inc.,
6009 Bandini Blvd., City of Commerce, CA 90040, (213)
722-9992 or 800 822-1996. Pre-etched pattern sheet available
in sterling, fine silver, gold and copper. They will do
custom etching to a depth of .006 - .008" (too shallow for
Graphic Chemical & Ink Co.,
728 North Yale Ave., Villa Park, IL 60181, (630) 832-6004 or
800 465-7382. Pre-sensitized copper, etching tank,
asphaltum, rosin, Z*Acryl nontoxic resist, hydrochloric acid,
nitric acid, ferric chloride, material for silk screens, rubber
gloves, goggles, photo etching supplies.
Kepro Circuit Systems Inc., 630
Axminister Dr., Fenton, MO 63026, 800 325-3878 or (314)
343-1630. Etching machines, screen printing supplies,
photosensitized copper, sodium persulfate, ferric chloride,
sulfuric acid, hydrochloric acid, stainless steel
electrodes. Very helpful sales people and a 'fax on demand'
service for MSDS's and instructions.
La Grande Industrial Supply, 2620
SW First, Portland, OR 97207, (503) 224-5800. Safety
Radio Shack, located in just about
every town in US. 42 degree Baume Ferric Chloride with a
dash of hydrochloric acid sold under the name 'PCB Etchant'.
Rio Grande, 7500 Bluewater Road
NW, Albuquerque, NM 87121, (505) 839-3300 or 800
545-6566. Asphaltum, etching resist, copper mordant, silver
mordant, Rio Master Etch-Press System, rectifiers, copper and
silver and stainless steel electrodes, protective clothing.
Thompson Enamel, P.O. Box 310,
Newport, KY 40172, (859) 291-3800 or 800 545-2776.
Asphaltum, PnP paper.
GC Thorsen, 1801 Morgan St.,
Rockford, IL 61102, (815) 968-9029. Etchant heater,
photo resist supplies, industrial Sharpie pens, drafting tape.
Alford, William. "Screen
Printing PC Boards." Electronics Now, September
1993. Instructions for making a screen to transfer a resist
Clark, Nancy, et al. Ventilation:
A Practical Guide. New York, Center for Occupational
Hazards, Inc., 1984. Practical help for safely ventilating
Coombs, Clyde. Printed Circuit
Handbook. New York, McGraw Hill, 1996. Complete
descriptions of imaging (getting the resist onto the metal), and
the science involved in the different etching systems.
Eisler, Paul. The Technique of
Printed Circuits. New York, Academic Press, 1959.
Explanation of the variables affecting ferric chloride; discussion
of screen printing.
Fastag, Miriam. "Experimental
Techniques for Acid Etching." Glass on Metal,
October 1994. Accounts of some less traditional acid resists
used in a class in Mexico.
Hiscox, Gardner (ed.). Henley's
20th Century Book of 10,000 Formulas. W. Henley
Publishing Co., 1942. Lists of formulas for everything from
etching acids to maple syrup - very interesting.
Kasten, Stephen. Electronic
Prototype Construction. Indianapolis, Prototype
Construction, 1983. Instructions for photosensitizing metal;
information on using ferric chloride and cupric chloride as
etchants and how to regenerate the latter; simple instructions for
building an air bubbler etching tank; directions for building a
screen printing setup.
Lewis Sr., Richard J. Sax's
Dangerous Properties of Industrial Materials, 9th Ed.
New York, Van Nostrand Reinhold, 1996. Lists of all the
known dangers of acids, solvents, etc., so that we can better
understand how to use and store them safely.
Lewis, Tony. "Make Your Own
Etching Tank." Radio-Electronics, December
1989. Step by step instructions for building a vertical
etching tank, incorporating an air bubbler and heater.
Nishioka, Alan. "Iron-On PC
Board Patterns." Electronics Now, September
1993. Instructions for using PnP.
Rossol, Monona. The Artist's
Complete Health and Safety Guide, 2nd Edition. New York,
Allworth Press, 1994. Suggestions for dealing safely with
all the potentially dangerous materials used in the studio.
Schwed, Antonia and Katharine Wood.
"Champleve Enameling." Glass on Metal,
October 1990. Explanation of the use of asphaltum resist and
ferric chloride mordant.
Strosahl, J.P., J.L. Strosahl and C.
Shaffer. A Manual of Cloisonne and Champleve Enameling,
Rev. Ed. Seattle, Self Published, 1996. Chapters of
silk screening asphaltum.
Wood, Katharine with Paul
Silverman. "A Revolutionary New Blockout Technique for
Etching Metal." Glass on Metal, August
1996. Instructions for using PnP Blue.