TECH: Making Your Own BRASS TAGS - BRASS ETCHING at HOME!

From:This Lawrence PDF
FERRIC CHLORIDE AND THE EDINBURGH ETCH

Ferric chloride can be used as a non-toxic alternative to nitric acid in the
etching process. It gives off no toxic vapours; causes little hazard during
occasional skin contact and gives an accurate bite. When ferric chloride is
mixed in solution with citric acid it becomes known as the “Edinburgh Etch”
and is suitable for etching most types of metals including copper, zinc, mild
steel, aluminium, iron and brass.

What is the Edinburgh Etch?

The Edinburgh Etch is achieved by simply adding citric acid to the ferric
chloride solution. This speeds up the biting effect. Also the addition of
citric acid prevents the build up of sediment inside the etched grooves,
which occurs when using ferric chloride on its own. Without the citric acid,
this sediment would have to be constantly removed so as to prevent it from
stopping the plate from being etched further. This can also be avoided by
the use of a vertical etching tank.

Notes on usage

Ferric chloride crystals need to be mixed with purified water into an initial
saturated ferric chloride solution. This can be stored indefinitely,
preferably in a closed container.
Do not use full strength ferric chloride on zinc plates as it works too fast and
can overheat and damage the fine detail when etching plates with large
open areas.
Before a fresh etch solution is used, the sting needs to be taken out either
by inserting a blank piece of metal or by adding a small amount of
exhausted acid.
When etching zinc, plates should be face up and require no agitation.
Traditional or acrylic (Z-acryl) resists may be used.
Do not use the same etching solution for different types of metal, always
use separate tanks or trays. If a metal plate is accidentally placed in the
wrong tank, this causes electrolytic processes, contaminates the ferric
solution, and in cases of zinc or aluminium plates, can lead to violent
chemical reactions.
In a busy workshop, the solution needs to be changed every ten to fourteen
days. Aquatints on zinc etch very quickly and so you should consider mixing a
weaker solution for aquatint.
When the etch is exhausted, it must be disposed of by taking it to a
chemical disposal company or by ringing your local council to see if the own
facilities for disposing of chemicals.

Recipes for the Edinburgh Etch

Zinc
Regular Edinburgh Etch for Zinc:
1 litre saturated ferric chloride solution (40%).
500g citric acid powder (can be reduced to 300g).
7 litres tap water.
Weak Edinburgh Etch for Zinc:
1 litre saturated ferric chloride solution (40%).
300g citric acid powder.
14 litres tap water.

Strong Edinburgh Etch for Zinc:
1 litre saturated ferric chloride solution (40%).
500g citric acid powder.
3 litres tap water.

Copper
The mixture is based on the overall ratio of;
4/5 saturated ferric chloride solution (40%).
1/5 citric acid solution which consists of 3/4 tap water and 1/4 Citric acid
powder.
This works out in actual quantities as for example:
6 litres saturated ferric chloride solution (40%).
1.2 litres tap water.
400ml citric acid powder (by volume) which equals 400g powder.
Steel
8 litres saturated ferric chloride solution (40%)
500g citric acid powder (can be reduced to 300g).
3 litres tap water.


Mixing: Edinburgh Etch for Steel
8 Litres
saturated ferric chloride solution (40%)
+ 3 Litres
tap water
+ 500 ml
citric acid powder (by volume) which equals 500 g powder


Mix ingredients as described for Edinburgh etch for copper.

Other Metals

Occasionally two other kinds of metal may be employed for etching purposes namely brass and aluminum. With respect to the quality of the bitten intaglio these materials are not a great extension of the possibilities provided by copper, zinc, and steel, but if etching is regarded as a sculptural as much as an illusionistic medium it is certainly worth experimenting with the fairly inexpensive silvery-grey aluminum and the gold coloured and fittingly costly brass.

Aluminum, which like zinc reacts vigorously with saturated ferric, etches well in trays of a medium dilute ferric chloride solution - normally one part saturated ferric chloride solution is mixed with 3 to 4 parts water. A small amount of citric acid can be added to this, but the non-sedimenting property is in this instance weaker than with other metals. The mordant exhausts itself quickly after a fairly vigorous biting reaction which once again involves the emission of hydrogen bubbles, and the generation of a certain degree of heat. Despite its fizzing nature the process remains controlled at this solution strength, and an open bite is etched within 40 minutes to 1 1/2 hours (note that the process accelerates with time). Aluminum plates always require thorough scrubbing with a stiff brush after etching to free the bitten intaglio structure from crystalline residues.

Due to its softness aluminum lends itself to mechanical work (i.e. drypoint etc.) but is less suitable for editioning as it is not resistant to the pressure involved in repeated printing. Brass by contrast, which is a very hard alloy of zinc and copper, can be etched in similar conditions as copper (see Edinburgh etch for copper) and is a very serviceable material for intaglio printing. It combines the graceful delicacy of copper intaglio with the robustness of etched steel - like steel its open surfaces also display a self texturing effect and plates do not due to their hardness, suffer from wear in large editions. However, due to the fact that it is more than twice as expensive as copper its use seems more justified when the plate is used not only for its printing properties, but also as an object in its own right.

The chemistry of ferric chloride

by Stephen Hoskins and Roy Pearce

Since Rembrandt, etchers have used nitric acid and Dutch mordant to etch copper. At the turn of the century ferric chloride solution was introduced in gravure work, principally because of its interaction with gum bichromated gelatine. With the increased emphasis on health and safety at work, we have had to reappraise these and the other chemicals we use.

The salt, ferric chloride, has none of the disadvantages associated with the other two acid etching solutions: it does not produce dangerous fumes, is odourless and, though corrosive, is not absorbed through the skin.

Ferric chloride solutions in water are strong acidic but in their reaction with copper no significant fumes or gases are produced. Simply, except in the presence of free oxygen, copper will not react to any significant extent with hydrochloric acid which is the acid produced with ferric chloride solutions.

The chemistry of the (etching) reaction

When ferric chloride is dissolved in water the solution becomes strongly acidic as a result of hydrolysis. The chemical reactions, in words and formulae are:


Schematic representation of the chemical interactions occurring during etching copper in ferric chloridesolution.

basically, ferric chloride in water solution ionises to iron (ferric) and chloride ions;



whilst the water ionises to hydrogen and hydroxyl ions;



The ferric ions will partially combine with the hydroxide ions to form ferric hydroxide, a compound which is only slightly soluble and precipitates from solution as a brown solid.



This precipitation can be regarded as removing hydroxyl ions from the solu-tion, leaving a relative excess of hydro-gen ions and it is this excess that makes the solution acidic. Because of a property of metals known as electro-negativity, copper replace iron from the solution and form a mixture of ferrous and cupric ions. Effectively the copper dissolves without producing any gas;



Ferrous ions become increasingly stable as the solution becomes more acidic and this helps the copper dis-solution to proceed more easily whilst in basic (less acidic) solutions the ten-dency is for ferrous ions to convert back to ferric. As more copper dissolves and the solubility limit is exceeded, cupric chloride precipitates from the solution, as anything from a green to a blue solid.

Strengths and mixing

Ferric chloride can be obtained either as a solid (not recommended as it can give off highly toxic hydrogen chloride fumes when mixed with water) or in liquid form when it is usually supplied in a strength of 45º Baume. This mea-surement equates to a specific gravity of approximately 1.43 or a weight to volume ratio of 39-41%. Purveyors of ferric chloride can use any of these measure-ments and often profess complete igno-rance of any form of the others!

To form the basic stock etching solu-tion, water is added in the ratio 2 parts water to 1 part ferric chloride solution resulting in a solution strength of 42º Baume.

Preparing the solution

At this stage the strongly acidic ferric chloride requires further treatment to remove free acid and to 'condition the solution'. Either small quantities of copper may be added and allowed to dissolve or (a more effective way) take 10 cc of the stock solution and add 10 cc of 9% household ammonia solution. This results in a sludge of ferric hydrox-ide which is allowed to settle before pouring off the liquid and adding the precipitate to 1 litre of the stock solu-tion. Once an etching cycle using ferric chloride has been initiated the third method is probably easier. Here spent ferric chloride liquor (containing ferric hydroxide) is added to the new stock 42º Baume solution, in the proportion 1 part spent liquor to 10 parts 42º Baume solution.

Colour in use

The optimum etching conditions usu-ally occur after some etching has been done (this reflecting an 'incubation' period for the chemical reaction to 'settle down') but as etching proceeds the solution becomes less effective. The progress of this exhaustion can be oh served by the colour changes - from an initial red brown (ferric hydroxide) through a turbid (muddy) brown (ferric and ferrous hydroxide) when the solution is working at its most effi-cient, and finally to a dark green solu-tion and black precipitate (cupric salts in solution and precipitated with the hydroxides). At this stage the solution is exhausted and requires disposal. This can be effected by the slow addition of either calcium carbonate (whiting) or sodium carbonate (washing soda crystals) - until effervescence ceases. At this point the solution is neutralised and may be disposed of safely.

The myth upside down

The normal recommendation is to bite copper plates in ferric chloride in-verted or on edge to avoid precipitated ferric hydroxide clogging the etched line, thus halting etching. However, there is little need for this if the plate is bitten face up' and removed from the solution every 20 min then washed in cold running water to remove the pre-cipitate before continuing to bite. This procedure does not present the hazard of other etchants and has the advantage of checking progress. Extremely deep bites or plates for relief etching are still bitten upside down. On completion of any biting, or if the plate is to stand between bites for any length of time, it should always be cleaned thoroughly with running water, since residual ferric chloride in bitten lines will continue to react.

Ease of use

To summarise, ferric chloride is a chemical and should be handled with respect. However, it does not present the level of hazard associated with nitric acid and Dutch mordant; indeed the only precautions necessary are to use goggles and gloves, keep the solution in a plastic bath, and wash off any liquid on the skin with water. Extraction and fume cupboards are not necessary.

A 42º Baume solution at its most ef-fective is very good for a deep line bite. When diluted to approximately 32º Baume by the addition of an equal part of water, it becomes very effective for soft ground and delicate work without a noticeable loss of biting time, and re-duces foul biting. Due to the low depth of bite necessary in aquatint, the strength of solution does not greatly affect time taken to create a black, therefore strength of solution tends to be a personal taste. The minus side is the length of time taken to bite a plate: half an hour in stock solution for a black aquatint, and an hour for an aver-age etched line. Very deeply bitten lines may take several hours.

Notes

1 To speed the process, some sources recommend agitation of the solution by bubbling air through an upright tank. Whilst this undoubtedly works there is a risk of hydrogen production by reac-tion with hydrochloric acid. Therefore either extraction or a constant and ade-quate flow of air is required to prevent hydrogen build up.

2 It is preferable to use industrial grade 45º Baume ferric for both cost and speed (obtainable in the UK from Ellis and Everard) these less refined solutions often bite faster and it is the safest way t&) buy the salt. Merck chemi-cals sell small quantities for laboratory use but this is the Analar pure grade at a 60% weight per volume ratio. This needs greater dilution to 42º Baume and tends to be a slower acting form of the salt.

Further reading
N.I. Sax. Dangerous properties of industrial materials, 1984. ISBN 0442-27373-8.
R.J. Lewis. The rapid guide to hazardous chemicals in the workplace. ISBN 0442- 01759-6.

Contact: Steve Hoskins, University of the West of England, Clanage Road, Bower Ashton, Bristol BS3 2JT, UK
Email S2-Hoski@UWE.AC.UK.

The Radio Shack PCB Etchant is, and i only take this on second hand knowledge, ferric and hydrocloric

I was able to use some of the solution to etch the NAMBLA memories from my cerebrum. (THANKS KIRK!)

Once clear of this nefarious stain I was able to complete my task of making some plaques for my good friend at Mayhem.



He seemed pretty happy with the way it came out.

If you're ever in San Diego, look up Mayhem. Everything from one-off customs and resto's to tires and service, Mayhem has got you covered.

BIG THANKS TO KIRK FOR POSTING THIS TECH!

this is nothing short of fucking awesome cant wait to try it thanks man

Many thanks for this post!!! One quick question....you mention a copier, could you send the design to a printer, from a computer, and print the PnP that way?

i want to make little plates for my toolboxes now. very cool.

Thespis: That should work just fine.

This is far and away the coolest how-to I've stumbled across. My head is spinning with the possibilities, just gotta wait for my PnP order to arrive.

Glad people are still digging on this. A couple pics of finished pieces are missing, but fuck it!

here is a cool vid on this - http://www.youtube.com/watch?v=8fBlYEKqsRo

Originally Posted by KIRK

Glad people are still digging on this. A couple pics of finished pieces are missing, but fuck it!

Man I've been itching to do this since you did this write up, can't believe I haven't yeat. Finally have a good reason, gonna whip something up next weekend, I'll post the results when we're done!

I've been "etching" to do this too

Any idea how much is bieng eating away per hour or so ?

I was planing to engrave myself a paire of brass pegs, but etchng might be the way to go !?

Great write-up

Awesome post - thanks heaps... went down to jaycar (Aus) for the bits and pieces. Couple of hours later - boom!



This is my first trial for a few little pieces.

Quick tips; I found out PnP sheets don't work in "Brother" lazer printers - which just happens to be the 4 printers I have access to!
Also I was having trouble finding brass sheet, without being special order. However if you look a lot of signs an stuff in hardware shops are on brass sheet. Back of these pieces are a toilet sign.

Originally Posted by tmb99

Awesome post - thanks heaps... went down to jaycar (Aus) for the bits and pieces. Couple of hours later - boom!



This is my first trial for a few little pieces.

Quick tips; I found out PnP sheets don't work in "Brother" lazer printers - which just happens to be the 4 printers I have access to!
Also I was having trouble finding brass sheet, without being special order. However if you look a lot of signs an stuff in hardware shops are on brass sheet. Back of these pieces are a toilet sign.

Nice!

I experimented with using leather dye on these. It gives a cool imperfect/aged effect and is WAY easy to sand off. It does need to be cleared over though.

Heres my first try at this it was pretty cool to watch it etch away the brass. Kirk what kind of leather dye did you use on those? The liquid or gel?

nice work!!!

Originally Posted by mzavala2424

Heres my first try at this it was pretty cool to watch it etch away the brass. Kirk what kind of leather dye did you use on those? The liquid or gel?

Liquid. It's pretty thin and doesn't want to spread evenly, which I like.

Here's another etched brass project I just finished for a charity art auction.

Thanks Kirk, I'm gonna try to find some I might try using some india ink too.