Etching

Etching is a method of removing exposed metal and retaining protected metal from a surface so as to create a design or texture. In our shop, we accomplish that with non-ferrous metals in one of two ways, both of which use a etching bath (mordant), a pattern that adheres to and protects the metal surface (resist), and a source of electrical current to initiate a chemical reaction. Parts of the metal are covered and protected by the "resist", while the exposed parts are eaten away by the electric current to reveal a design.

The Jewelry and Metal Craft Shop currently supports two methods of etching non-ferrous metals: salt-water etching and electro-etching.

Salt-water etching

Equipment and supplies

Clear jar with wide opening (e.g. pickle jar) deep enough to submerge your piece vertically

Salt (don't use salt that has anti-caking agent)

Water (Distilled, preferred)

Copper wire - 16g, 2 ft. cut in half

Pliers

Drill with 1/16” bit or metal punch

Oil paint pen or PNP paper, (optional)

Metal sheet - brass, bronze, copper

Timer

Hard, very flat surface, heat-resistant

Sheet of paper folded

Flat household iron (They actually do still exist.)

Laser printer (uses toner, not ink) if printing to PNP paper. Note: Brother laser printers do not work.

Battery - one or two "D" cells, with battery holder and leads with clips

3M green scrubby pads

Brass brush

Packing tape

Acetone or nail polish remover

Cotton balls

Procedure

Initial Set up

Salt water solution

Batteries and leads

Cathode and wire

Container with clean water, large enough to rinse piece

Soft brush to clean residue from surface during etching

Image to etch

• IMAGE: Black and White ONLY (not grayscale)
• Print to PNP (Print and Peel) sheets
• OR
• Use an oil-based paint marker (e.g. Krylon paint pen)

Prep your piece

• Flat iron - set to ~300 deg. F (wool-cotton)
• Metal piece should be larger than the image by 1/4” minimum all the way around
• Drill a 1/16" hole (or just large enough to accept the size wire you have) within the 1/4" margin around your piece. Remove any burs so piece can lay flat
• Clean your metal (copper, brass, nickel) thoroughly to remove all oils and dirt

Add the resist

The resist is what the oil paint or the toner from the PNP paper does. It protects the parts of your image that you don't want etched. It resists being etched!

• If you will be drawing a free-hand design, use the oil paint pen and go for it. Try not to touch the face of your piece with your hands in the process. Let it dry, then skip down to the next section.
• If you will be transferring the image from your PNP paper then you need to trim your image to fit completely within the boundaries of the metal sheet, allowing a 1/4" margin on all metal edges.

• Place the PNP image, toner side down, on the metal, insert both into the folded sheet of paper. Lay the metal "sandwich" onto the firm, heat-resistant surface and firmly press the hot iron flat down on top so as to heat the toner on the PNP enough to transfer and adhere to the metal surface beneath. Begin timing this for about 20 seconds. Timing can vary significantly depending on the temperature of the iron and the size of your piece. Move the iron in small circles as you press down flat. After 20 seconds, (or whatever timing you have learned works for you) remove the heat, use a spatula or tongs to lift out the hot metal and hold it under cold running water. Carefully lift off the PNP. If the transfer is successful, the toner areas from the PNP will have transferred to the metal leaving a transparent area on the PNP. That toner area is where the metal will not etch. If bits of toner failed to transfer, use the oil paint pen and touch it up.
• To protect the back and edges of your piece from etching, use the packing tape. Use enough tape to cover the back of your piece, extend over the edges and just into the margin of the front side. Trim tape to fit.
• Feed one end of the copper wire through the drilled hole, fold it back and wrap it tightly around the wire to form a loop. Press the loop against the metal surface to make contact. Remove bits of the tape as necessary to make a good contact. Place the metal piece into the jar of salt water. With the remaining length of wire, form a hook over the jar edge at a length that supports the piece to hang completely submersed in the salt water. Leave a few inches of wire hanging over the outside for the battery to be connected. Excess wire can be cut off. This is the "anode" or where the positive (+) battery lead is connected.
• The second sheet of metal will be the "cathode" or where the negative (-) battery lead will be connected. It should be of the same kind of metal and least as large as the piece you are etching. As you did with the anode, drill a hole in one end, loop and fasten another piece of copper wire through the hole. Hang this metal piece in the saltwater opposite the anode and not touching it.

Etch It!

• Attach the positive (+) battery lead to the anode wire (your piece) and the negative (-) battery lead to the cathode wire. This completes an electrical circuit and you should start to see tiny bubbles forming on the cathode metal sheet. That shows that the chemical reaction is happening and the exposed parts of your piece are starting to be etched away.
• Check your piece after 20 minutes. Unclip the anode battery lead, lift out your piece and rinse it in water. You can use a soft brush to lightly remove residue from the surface. Using your fingernail, carefully check the depth of the etch. If a deeper etch is desired, place the piece back into the saltwater and reconnect the anode lead and time it again. When the etch is satisfactory, unclip the battery leads and rinse the piece. Remove the resist with Acetone (or nail polish remover) and cotton ball.

Electro-etching

Equipment and supplies

Etchant (mordant) - Copper Sulfate (e.g., "Root Kill"),

Plastic container,

Electric current source (e.g., manual battery charger, Rectifying power supply) with leads/clips

Copper wire ~ 16 g

copper or brass sheet

3M green scrubby pads,

brass brush

duct or packing tape

Procedure

This procedure is similar to the saltwater etching. In this case it is best to suspend the metal in a way that allows even coverage of the area to be etched. The metal can be suspended using thick styrofoam, as it floats. It is also recommended to employ some form of slow movement in the mordant while etching. This keeps the mordant moving evenly over the surface of the metal, allowing for an even etch over the whole surface. This mordant is much faster at etching and is possible to etch all the way through the metal in a very short time depending on the thickness.

• • More info to come**

References

Electrolytic Etching Copper and Silver Using Copper Nitrate, a replacement for Table Salt (NaCl) by Ben Dory. Published by SNAG (Society of North American Goldsmiths) http://www.snagmetalsmith.org/wp-content/uploads/2015/11/TechArticle_Nov_2015.pdf