Etching Metal Part 2: The "Salt" Etch

This three part post on etching is in conjunction with my upcoming demo for the Metal Clay Artisan Guild in Connecticut.

The above etched cuff is a great way to start learning to etch.  It was a scrap of copper roofing material that was "sandwiched" in masking tape.  I cut the design out with an exacto knife from the tape and used an aquatinting technique for the resist in the background to create the texture.  If you follow the link here to my last blog post, you can learn all about different resist techniques to get your design on the metal.

As I discussed in my previous post, my etching experiences began a very long time ago with materials like nitric acid and asphaltum.  Today there are much safer etching and resist solutions.  For etching in this post, I am using Ferric Chloride, also known as the "salt" etch.  Ferric Chloride is not an acid, so rather than dissolving the metal, it agitates it and pieces fall out.  Here is some more information from Printmaking Today that discusses the use of Ferric Chloride in the art studio, just follow this link.

Supplies

I use the following materials when etching:

-Saefty Glasses, Rubber Gloves & an Apron

-2 Plastic/Disposable Bowls

-Floral Foam or a Sponge (a disposable object that floats)

-Duct Tape

-Ammonia

-Your prepared Copper

-Ferric Chloride (also known as "PCB Etchant")

Ferric Chloride can be purchased online from a number of jewelry supply companies, but if you can find it locally at a Radio Shack, you will avoid a hazardous shipping fee.  Also, I prefer to purchase chemicals in the smallest quantities necessary until I know how much I am going to use.  This saves me from have a huge stock of a chemical that I need to responsibly dispose of.  Radio Shack sells it for etching motherboards and a pint is around $11.  For jewelry work, a pint will last you quite a while.  Follow this link here to check it out at Radio Shack, if it's not in stock you should be able to select "ship to store" for free. 

     

Safety First!

Ferric Chloride is a salt and not an acid, so you do not have to worry about it being absorbed by the skin.  It also does not give off or produce toxic fumes, so is a great alternative.  With that being said, the rule of thumb for all chemicals is:  Safety Glasses, Apron, Rubber Gloves, Close Toed Shoes and Ventilation!  On a side note, it will stain everything it comes into contact with a dark, sludge green color.  It will take weeks to get it off your skin and nails and it will not come out of clothes or countertops, which is why despite its safety you really want to wear gloves and an apron.  As you pour it and work with it, consider the same precautions you would take with a large bowl of liquid black ink.  The black ink will stain less.

Prepare to Etch

The first time you etch you really need to do a test strip to see how fast your etchant is working and to determine how deep you want the etch to be.  For the discs with the birds on it in this series of posts, I used 22 gauge copper and wanted to find an etch depth that would be deep enough to use as a texture plate in metal clay.  I cut a test strip out of copper the same thickness as the final pieces I was doing.  Coat the back with clear nail polish to protect it.  On the front, using a permanent marker as a resist, draw a border and divide the piece into 4 boxes.  Number each box (1-2-3-4) with the marker as a resist.  You can see my finished test on the right, it has a textured background.  I did 30 minute increments, took the piece out, rinsed it then covered each number/segment with duct tape to protect it from further etching and placed the piece back in the solution.  If I have not etched in a while or I am etching a new project, I always run test strips.  It is a cheap way to ensure I do not ruin a piece, it only takes a few extra minutes to etch all the way through and have a hole in your piece!

To etch the piece, pour the Ferric Chloride solution into a plastic or glass container, 1" should be more than deep enough.  Once an item is used in the studio, it can never go back to the kitchen, so these containers should be marked or disposed of, this is an easy clean up so they can be reused for more etching in the future.  Keep it small - the container only needs to be slightly larger than what you are etching.  Cut a piece of floral foam or a sponge a little bigger than your piece.  Wrap a piece of duct tape around the foam with the sticky side OUT.  Wrap another piece around three of the four sides to cover the sticky sides so you can handle it.  Use rubber gloves to place your piece with its back pressed firmly into the sticky tape.  Remember, at this point the oils from your fingers could ruin your design.  Then place the piece in the container and give it a press.  It should bounce back and gently float around.  Since the salt agitates, but does not dissolve the metal, it is a good idea to tap it or gently agitate it while it is etching to make sure the pieces are falling out and giving a clean etch.  While your piece is etching, get a bucket of water to rinse it in and have it partly filled next to your solution.

Final Etch

When the time is up, based on your test strips, pull the piece out and rinse it in the water bucket.  Next take a clean sponge with some Ammonia on it and rub the piece to stop the etch from continuing.  Pull the pieces off the foam.  The pieces may need to be clean with acetone (or nail polish remover) to get the rest of the resist off.  You can see here that the etched piece has a "starburst" effect in the background.  Since the metal is not being dissolved, large areas are often left with this effect.  The best way to control a large open area is with the aquatint resist technique.   I find that Ferric Chloride solution has about 5 hours of etching time for me, which equates to 2-3 times of use.  I also use it all at the same time, so I might etch some pieces, cover the solution and then be sure to either use it or dispose of it within a week.  After that, you just don't know if you will get the same results from it and I don't think it's worth the risk of ruining a piece with potentially spent etchant.  I have successfully used ferric chloride from the same original bottle for years, so it does have a long shelf life until activated.  Check out the final blog post in this series to see how these copper discs can be used as texture plates.

Disposal

The Ferric Chloride should be neutralized with baking powder.  Allow any solids to settle and drain off any neutralized liquid into your rinse bucket so that it is diluted and flush down the toilet.  The remaining solids or sludge should be poured into a plastic sealable container, clearly labeled, and disposed of at your local hazardous waste disposal facility.

Etching Metal Part 1: The Resist

This three part post on etching is in conjunction with my upcoming demo for the Metal Clay Artisan Guild in Connecticut.

I have been working in metal for almost two decades and it all began with etching.  During a printmaking class in high school I learned to etch zinc plates with Nitric Acid for intaglio printing and fell more in love with the surface qualities I could create in the metal than the final prints.  I have used these basic techniques for years in my own work and in my classroom.  From printmaking, to sculpture to jewelry, the technique is relatively the same, it just varies in size- also, today I have found safer materials to work with than nitric acid and asphaltum.  The information in these next two posts is what I use to successfully etch copper, nickel and brass metals.

1.  Prep Your Designs & Your Metal

Start by figuring out what you will eventually use the piece for.  Will it be the actual piece of jewelry? Maybe it will be a stamp for polymer work? Maybe it will be a plate for embossing paper?  Or maybe it could even be a texture plate for metal clay?  In any case, you want to determine your size and draw or print the original artwork or copyright-free image you are using the exact size and shape you will eventually etch.  The cleaner and sharper your image is, the better it will work in the end.

Prep your metal by first cutting it to a size slightly larger than the design you want to etch, it also must be flat.  Next, clean it with a super fine steel wool pad to remove any oils that might disrupt the resist or the etch.  After this point, be careful not to touch it with your fingers, only hold it by the edge.  Immediately before you apply any of the below resists, wipe the piece down with rubbing alcohol.

2.  Create Your Resist

You will need to create a "resist" on the surface of the metal to protect the part of your design you would like to keep raised.  The etching process removes the metal that is left exposed.  You can etch sharp clean lines or large backgrounds can be removed.  This needs to be decided during your design.   There are many ways to create a resist on the metal, here are three simple and safe materials to use as resists.

PnP Resist (Press-n-Peel blue acetate film)

If you have a very precise image or are trying to transfer a photograph, one of the best ways to get your image on the copper is using PnP paper.  You can photocopy your image to the matte side of the PnP paper using a copy machine with a carbon based toner.  In my experience, printer ink does not generally create a successful resist.  You will then iron it on to the metal with the matte side facing down to create a resist, as you iron and the image becomes more and more visible through the acetate, the resist is transferring.  When the metal has cooled, pull up a corner of the PnP to check your design, if you need to you can lay it back down and keep ironing.  If there are small areas that need to be touched up, you can fill them in with black permanent marker or nail polish.  You will need to protect the back of your design with contact paper or electrical tape and then seal the edges with nail polish to prevent them from being etched.

There is a great article on PnP you can find on the Ganoskin Project site that you can follow a link to here.

Tips for PnP Resist:

-Run the copy machine until you can get the darkest (and cleanest) copy possible on white paper before copying on the matte side of the acetate.

-Be prepared to test your iron on scrap metal.  Since every iron is different, you will need to have some extra PnP and scrap metal to do test strips.  My iron at home requires the highest setting for almost 10 mins to get the small size transfers in this post, the iron in my classroom requires a lower setting and less time.  Begin on your highest setting and move the iron in circles until the image becomes clearly visible or the acetate buckles.  If it buckles, turn the iron down.  Hold the acetate with tweezers down in one corner and peel up with another pair of tweezers from another corner to check transfer.  Continue ironing as needed.  I generally time my test strips in 3 minute increments.

Tape Resist 

Using either masking tape or clear plastic packing tape, make a "tape sandwich" with your metal in the middle.  Make sure to seal all the way around the edge, this will stay in place during the etch to protect the back and sides.  Rub the tape down to remove any air bubbles. Then either draw or tape your design on top of the tape, leaving a border of tape to protect the edge.  You will then use an exacto knife to cut out your design.  In this case, I am cutting the design and removing it in order to etch the lines of the designs.  The tape will be left on the background area to protect it.

Permanent Marker Resist 

Choose a high quality permanent marker and draw your design directly on the clean metal.  Make sure it is a rich, solid black with no transparent areas.  Make sure there is a border to protect your edge and seal your back with either electrical tape or nail polish.

Aquatint Texture Resist

The same technique used to etch printmaking intaglio plates to create a stippling effect is great to create a texture background to hold a patina.  You can either use it to create a simple texture piece or in the background of any of the above resist methods.  Simply spray a mist of spray paint LIGHTLY across the back of the piece of metal in a quick sweeping motion.  This should leave "dots" randomly across the surface.  Experiment with the density of the spray and the effect you get from the etching, this is another time you will need to do test strips to get your desired effect.  Here, I drew an image with permanent marker and "swept" it with spray paint to create the dots in the background which will be our texture later on.  You can see how light it is, the darker it gets, the more you are blocking out the etch.  Don't forget to protect your edges and your back.

If you want to learn more about etching methods in printmaking, check out the great site artist Julie Niskanen has on intaglio process by clicking here.

3.  Etching the Metal

Once you have prepped and applied your resist to the metal, visit my next blog post (here) to learn how to complete the etching process.

Same Technique, Different Sizes...

All of these pieces were done using the etched copper method in this blog post.  These were all specifically done using a masking tape resist, as described above.  From the 6' long hanging sculpture (right) to the 14" x 18" framed etching (left) to the chunky cuff bracelet (above), the same method has endless possibilities.