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Etching metal is very simple. It involves a mordant (acid) and a resist to that acid. The resist can take many forms, plastic, vinyl, marking pens, duct tape, nail polish, etc. As long as it resists water, the procedure will work well. With current photocopy technology and computer laser printer technology, you have more flexibility in your designs. These are basically the same techniques as printmakers use with zinc, but with brass, copper or bronze and silver, you have options for additional fabrication choices involving solder or cold connections.
Why use the photocopy transfer technique? One it is very cheap. The overhead transparencies are 100 sheets for about $25. Two, it doesn't matter which side you use and it does not take any special equipment. There are other great products on the market such as PnP Blue, and Imageon. This works well for me, and one can use these protocols even at home.
It is important to note however, that designs that have good contrast will work the best. I like the Dover Books that have no copyright issues. If you have a laser printer, the clipart disks are wonderful.
Nitric/Hydrochloric Acid vs. Ferric Chloride/Nitrate
Ferric Chloride and Ferric Nitrate are slower etches and have extra safety features. Nitric or Hydrochloric acid etching goes much faster and is very hazardous. It has its points, but for this purpose, I like the easier method.
While safer than nitric, these are still considered hazardous, so close attention to the process is important. I have outlined safety issues when necessary.
One great feature of the acid etch is the incredible textures you can achieve by the action of the acid playing on the surface of the metal. Somewhere between Repousse and chasing, depending on the depth of your etch, can be achieved.
It is important for anyone to use good quality Safety Glasses when handling etching liquids. Also, a pair of household, well fitting gloves is a good idea.
Ventilation is also a good idea. Tips on disposing the etching solutions and the Material Safety Data Sheets (MSDS) are at the end of the protocol.
- A small Rubbermaid or other plastic tub, the size of a shoe box, with a tight fitting lid
- Ferric Chloride (for bronze, copper and brass); Ferric Nitrate (for silver)
- Duct tape and two sided sticky tape
- Red Staedler ink pen (available at Office Depot, Staples, Charette) or any drafting supply store
- Cheap air pump from a pet store
- Metal - 20-16 gage
- 3M PP 2200 Overhead Transparency Film
- Paper towels
- Curved burnisher or spoon
- Mix of water and denatured alcohol, 2 parts alcohol, 1 part water in a tight fitting jar
- 3M Scotchbrite pads, and a degreasing cleanser such as Comet or Ajax or Penny Brite (the best)
- Cheap pancake griddle. A new one will run about $35, but finding an old one in a thrift store is perfect
- Baking soda
- Safety glasses, rubber gloves
- Household ammonia
Process: Image onto Metal
1) Select your metal. Start with a piece of metal, no larger than 3 x 3 to begin. File any corners or rough edges until they are smooth. Clean your metal with Scotchbrite and cleanser or Penny Brite until water runs off your metal in a sheet. If you see the water beading, then clean again. Scrubbing with Scotchbrite will serve to give the metal a "tooth" and will clean it well. Dry with a towel and handle by the edges.
2) Select your image and photocopy onto the PP 2200 overhead transparency film. Images should be high contrast with visible distinction between dark and light. The grey parts in between can make it difficult for the acid to bite. Trim your picture so there are no overlaps from the film over the metal. It's best that you leave a little extra metal around the edges. Laser Printers vs. Inkjet Printers: Laser printers are basically small photocopiers. They use the same kind of toner and scanning technology. Inkjets use water-soluble ink that will NOT work for this process.
3) Heat your iron to "cotton" and your griddle to 250 degrees F. Depending on the kind of iron you have, you may have to adjust the heat. Overhead transparency film is designed for very high heat, but some irons are extremely hot. I suggest some tests first.
4) Put one piece of your paper towel on the griddle. This is meant to protect the griddle face, and also keeps the metal from skating around. Many griddles have Teflon coatings these days. Don't worry about the paper burning. If you remember your Ray Bradbury book, Fahrenheit 451, paper doesn't burn until 451 degrees F.
5) Lay out all your supplies, the burnisher, tweezers, alcohol and paper towel next to you for easy access.
6) First take a small wad of paper towel and saturate it with the alcohol mixture. Clean one side of the metal and the TONER side of your image. IMPORTANT!! and this is the trick to making the whole process work for you. Make sure when you place the image side down to the metal, that it is still wet. Squeegee out the excess moisture and any air bubbles by rubbing your hand across the metal and film. It doesn't need to be dripping wet, but it does need to be wet.
7) Immediately place the metal with the film side up onto the paper towel already warmed on the heated griddle. Immediately place another paper towel over your piece and your iron on top of that. Let the iron sit for about one minute. Carefully iron the piece for about 20 more seconds and lift the iron. Remove the paper towel. Place the burnisher in one hand and a tweezer in the other. Carefully lift one corner of the film and see if the image has transferred to the metal. If it hasn't, replace the film and keep heating. Sometimes, using the burnisher will help. Burnish the image onto the metal. If it has transferred, remove the film, WHILE HOT in one smooth stroke. Voila, you have your image. If it smudges, then the iron is too hot. Try decreasing the temperature. The nice thing about this process is that you can scrub the image off and try again. This will take a bit of practice, but in the end, you should get it to work very well. Transfer the metal to a heatproof surface. A metal block or anvil works nicely. Once the toner is on the metal, it is very stable. I have had sample pieces that have been sitting around for years that are as good as the day I ironed the images down.
8) Troubleshooting. Sometimes the image does not transfer completely. This is where your red pen can help out. You can fill in some areas before the etching. Thicker gauge metal takes longer to transfer than thinner. Large metal pieces can work, but you must raise the griddle heat and spend more time ironing. As a rule, I don't try to use multiple pieces of film on one piece. If the metal cools too much, the film will pull back the image. You can however, do multiple images in stages. Silver heats up faster, so watch your temperatures carefully. Remember, hot metal looks just like cold metal.
Now that you have your image, you are ready to etch. Lay out your supplies, acid, tub, duct tape, Styrofoam, two sided sticky tape, safety glasses and rubber gloves, and the air pump.
1) Your metal should be clean. Use Penny Brite (citric cleanser) or regular cleanser. Don't scrub this time, rather mix a solution in water or sprinkle the cleanser over the metal and rinse with water. You can GENTLY move it around, but don't use any pressure. Dry in a clean paper towel and leave covered.
2) Tape the back with duct tape. Place two strips of double sided sticky tape onto the duct tape. Cut a piece of Styrofoam to fit the size of your metal. Compress the two together until it sticks.
3) Strap the air pump onto the side of your plastic tub. I actually like to make this fixture, but using Velcro adhesive tabs. This is very helpful and the gentle vibration won't dislodge it. Why an air pump? These cheap pumps are made to vibrate for long periods of time. This vibration facilitates the etched residue to fall to the bottom of the tub and keeps the exposed area of metal etching continuously.
4) Donning your safety glasses and gloves, pour the ferric chloride into the tub, about 1/3 full. Try not to create bubbles, but a few are ok. This should be performed in a well-ventilated area.
5) On the Styrofoam pontoon, write the time you began your etch. Strap the pump onto the side of the tub. Carefully lower the metal into the solution. The Styrofoam act like little pontoons and make sure that the metal is submerged correctly. Close the lid and plug in the pump. Etching should take about 45 min to 1.5 hours, depending on the depth of etch you desire.
6) Check the progress of the etch every 30 minutes. Have a separate empty container nearby. Pull the metal out and take it to a sink. Rinse thoroughly. The small amount of ferric chloride isn't enough to harm the sink. Flush with water and rub your finger along the metal to see how the bite is taken. If you need more, drop it back into the tub.
7) Etch done? Pull your piece out of the acid, drain well and bring it to the sink. Fill your container with water and about a handful of baking soda. This will neutralize the acid. Wait a minute after it stops foaming. Rinse well. Refill the tub with a little more water. Add about 1/8 c of ammonia. This acts as a stop bath for the acid and completely arrests any leftover or trapped acid. Under running water, or submersed, pull the tape off your metal. Clean the metal again with the Penny Brite or cleanser and use Scotchbrite. This will scrub off the last of the toner. Now you are ready to use your etched piece.
Q. What kind of acid etches what kind of metals?
A. Ferric Chloride: Etches copper, brass, and bronze. Ferric Nitrate: Etches silver
Q. Is the procedure any different with silver than copper?
A. The protocols for etching copper are exactly the same as copper.
Q. What is Penny Brite?
A. Penny Brite is an excellent copper cleaner that is made from citric acid. It leaves no greasy residue behind and is the recommended cleaner for this process.
Q. How do the chemicals arrive?
A. Ferric Chloride can come in crystal form or pre-mixed. Ferric Nitrate comes in crystal. Lists of suppliers are below.
Q. How do I mix the chemicals?
A. Ferric Nitrate is mixed with 1-part Ferric Nitrate crystals and 2 parts distilled water. Make sure you ALWAYS add the crystals to the water only. Ferric Chloride
Q. Can I use regular tap water?
A. No. The chemicals in tap water vary from city to city with different additives. Use distilled water whenever possible.
Q. How do I dispose of Ferric Chloride Solution?
A. There are two ways:
- Contact your local Hazardous Waste Disposal Company
- The solution must not be put down the drain because of residual copper ions left in it. To make it safe for disposal, you can add sodium carbonate (washing soda) or sodium hydroxide to it to neutralize it, until the pH value goes up to between 7.0 and 8.0, testing it with indicator paper. Copper will be deposited as sludge. Allow the sludge to settle, pour off the liquid, further dilute it with water and then it can be poured down the drain. Collect the sludge in plastic bags and dispose of it as required by your local waste authority.
- Ferric Nitrate
Ferric nitrate solution is a corrosive liquid. Avoid contact with eyes, skin and clothing, and do not inhale its mist. The solution can decompose at temperatures below 100°C (212 F) to yield toxic nitrogen oxide gas.
As with any chemical, ferric nitrate requires care in handling. Anyone responsible for the procurement, use or disposal of this product should familiarize himself and those handling the product with the appropriate safety and handling precautions. This information is available in the Material Safety Data Sheet, which may be obtained by contacting our Customer Service Group.
Q. Where can I purchase Ferric Chloride or Ferric Nitrate
Ferric Chloride: Graphic Chemical and Ink Company , Zacryl.com
A. There are a few sources out there. Ferric Nitrate is often used as a patination for sculptors.
Ferric Chloride and Ferric Nitrate: Bryant Laboratory, Inc.