IMPORTANT UPDATE: Since posting the information below regarding the use of kosher salt for etching metal, I have continued to research the technique and now know that I was right to question the safety issues involved. I stopped using the salt and will be switching to using copper nitrate instead. Anyone interested can read about this in the excellent, well illustrated 13 page PDF created by Ben Dory.
Once I have it all up and working again, I’ll post my results.
Anyone interested in etching metal in their own studios should read this excellent book first. Coral Schaffer covers a great variety of techniques, including (but not limited to) electro-etching. In particular, I value the safety information provided for the various methods included in the book.
In reading many blogs and posts related to electro-etching with salt water and some power source (including batteries), I see that most think of the salt water methods as “safer” than methods using ferric chloride. This is a misconception in my opinion. While salt water may be less messy, cheaper, and easy to make, it is only as “safe” as the methods used. It still results in copper dissolved in a solution that is bad for the environment, not safe for contact with skin, eyes, etc.. The copper rich salt water must be disposed of at a hazardous waste drop-off location.
If you etch with salt water, follow all safety instructions carefully. Gloves, eye protection, good ventilation, and proper disposal of copper rich water.
February 18 Update:
With the goal of making an easier, faster, and better connection of the piece to the lead, I cut a sheet of copper to tape the piece to. This eliminated the need for holes drilled in the piece and the time it takes to attach and form the wires that connect the piece to the tube used to hold it for suspending in the tank. This worked as planned and made it very quick and easy to remove one piece and tape on another with no waste of copper wire. Much less messy as well.
Photo below shows the tank with the current switched on. I’ve etched a couple of pieces in this bath and the crud is really building up. Note how much is floating on the surface! Seems to work well all the same. Update: February 21 Just learned that this “crud” is “sodium hydroxide (lye) and copper chloride”. After the etch bath sits overnight, this crud settles to the bottom of the tank. I syphon off the clear solution to re-use (with added salt) and pour the crud into a bottle to take to the hazardous waste site. I am very careful to wear proper gloves to protect my skin at all times. Also safety goggles…. just in case.
Photo below shows the piece taped to the latest version of the anode support. All areas not to be etched are covered in clear packing tape EXCEPT the piece that hangs outside the tank where the lead is clamped. The oxides/patina visible on the back of the piece is from a previous set-up where I taped wires to the piece and the salt water leaked in next to the wire.
Win some, lose some.The continuing saga of the electro-etching experiments. This time using Kosher salt and distilled water.
In my enthusiasm, I purchased two power sources. The fancy one with the digital read-outs, dials for controlling both amps and volts, lots of available power. The price from Amazon.com was very good ….$60 plus shipping…. and if it had worked, I would be very happy with it. Unfortunately, it was defective and I returned it for a refund. At first I thought it was operator-ignorance causing the failure, so I had Sky bring in an amp/voltage meter to check it.
The less fancy, less powerful, and less expensive (about $33) one works very well. At least on the size of piece I etched with it yesterday. It remains to be seen how it might work on a larger piece in a larger container. It works at a steady, pre-set 2 amps. I set the adjustable voltage to its lowest option of 3 volts.
This one works:
Note: neither power source came with the required leads. I had to buy these from another seller on Amazon.
I modified the anode following Sky’s suggestion that more edges would result in a faster etch. I also made certain that the connection of the copper wires to the piece were very good.
I used the smallest container I could find that would hold the piece (anode) and the cathode. The photo shows how the water looks the day after it was used for etching. Dissolved copper sinks to the bottom, a little junk floats. When the etching is happening, the water is very murky after a short while.
With all of these “improvements”, I was able to etch the 18g copper to the desired depth in a reasonable amount of time…. two hours. Next, I’ll try to etch larger pieces in a larger tank to see how this small power source handles the job.