Etching can be the first step (or the finished product!) in creating beautiful metalwork pieces. The basic process is very simple: a resist is painted on the metal, is allowed to dry, and then the piece is immersed in an acid/water solution and allowed to sit for a period of time until the acid has eaten away at the exposed metal. The most difficult part of the process is safety.
ADDING ACID TO WATER IS ALWAYS SMARTER!!!!!!!
This should be your mantra when working with acid in any form. Adding water to most acids is very unwise, as the chemical reaction produced is HEAT... very rapid heat that can, on occasion, cause an explosion of the solution. Common sense when working with acids and metals is a necessity.
Resist - anything that will keep acid from reaching the metal. These can include Sharpie marker, beeswax, asphaltum, grease pencil, nail polish, spray paint, commercial acid resist products like Cov-R-Cote, masking tape, etc. Some resists work better with some acids than with others. A little experimentation is necessary to find the best one for your project, but I have found that Sharpie marker gives a really good resist with most acids, and is precise when designing an elaborate etching pattern.
Mordant - a solution of acid and water used for etching metal. NEVER POUR AN ACTIVE MORDANT DOWN YOUR DRAIN! If you must dispose of a mordant (if it has gotten too contaminated to work effectively), please dilute it down with water, add some baking soda and pour it into the ground.
Materials Needed -
metal - copper and brass give good results
acid - make sure to use the proper acid for your metal
water - LOTS of it!
baking soda - LOTS of this as well!
glass dish with an airtight cover
abrasive cleaner (like Comet or Ajax)
a feather or very soft small paintbrush
Rules of the Road
Make sure you work in a well ventilated area.
Wear rubber gloves to protect hands.
Mix the mordant at least an hour before you start etching. Acid and water are slow to mix.
Use only glass containers with sealable lids to keep acids and mordants in.
Generally, you will find acids in three grades: chemically pure (don't even try to get this one - usually only found in chemical labs) which is 100% pure acid, reagent which is 70% acid, and commercial which is 50% pure acid. Reagent and commercial acids are the most readily available, so you may want to use a stronger concentration of them in the following formulas, but just increase the acid by a small amount.
GOLD 1 PART NITRIC+3 PARTS HYDROCHLORIC
STERLING SILVER 1 PART NITRIC+3 PARTS WATER
COPPER, BRASS, NICKEL 1 PART NITRIC+1 PART WATER
ALUMINUM 1.5 OZ. AMMONIA+5 GRAMS COPPER SULFATE +14 OZ. SODIUM HYDROXIDE (this is a salt and not an acid) +2 GALLONS WATER
LEAD, TIN 1 PART NITRIC+4 PARTS WATER
IRON, STEEL 2 PARTS HYDROCHLORIC+1 PART WATER
Ready to start? Good! Using a glass container (Pyrex works well) that is deep enough to completely cover the sides of your piece of metal, and wide enough to allow it to lay in the bottom, slowly mix your mordant, adding acid to water where applicable according to the above listed formulas. Make sure you mix enough to completely cover your metal. Set the mordant aside while you cover your metal with a resist.
Clean your metal thoroughly with the abrasive cleaner and water. Try not to touch the metal with your fingers after it has been cleaned as the oils on hands can act as a resist and give you an uneven etch. Hold it by the sides or wear cotton gloves when handling clean metal.
If you are doing a one sided etch, cover the back of the metal completely with resist and allow to dry. Sketch your design on the front of the metal in pencil and then paint or draw over the parts to remained raised with resist. Allow to dry and then add a second coat of resist to the raised areas. Allow to dry thoroughly.
Wearing rubber gloves, drop your piece into the mordant. The etch produced by a new mordant will be pretty slow most of the time. You will see bubbles start to form on the areas of metal not covered by the resist. You must keep a close eye on these (careful not to breathe in the fumes) and brush them away with the feather or paintbrush. The bubbles, if left on the piece will act as a resist and will give you an uneven etch. Make sure you do not brush away the resist when you "feather" your piece. Do it very gently.
When the etch is as deep as you want (shallow for simple patterning, deeper if it is to be used as a base for enamelling), use the copper tongs to remove the piece from the mordant. Rinse it under running water for a few seconds, then use the abrasive cleaner to remove the mordant. You can now polish the piece or add enamel to the sunken areas, attach it to something or do whatever you like with it.
Be careful and have fun!
The Complete Metalsmith by Tim McCreight, ISBN# 0-87192-240-1
The Encyclopedia of Jewelry-Making Techniques by Jinks McGrath, ISBN# 1-56138-526-3
The Design and Creation of Jewelry, by Robert von Neuman, Radnor Publishing, 1982.
ARE, Inc. (800)736-4273
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