Monday, September 2, 2013

Etching, salt, citric acid and batteries

I have been remiss... well that isn't the right word.... downright horrible about blogging.  I don't promise to do much better, but I do promise to try.

Thanks to Ann Sanicola,  I have been learning to etch with salt water and batteries.  I have done a lot of experiments, and thought others might like to see this


  • copper
  • resists (PNP, sharpie, stazon, oil paint, fingernail polish) anything to block the design from the etchant
  • brine water (distilled water boiled with kosher salt until it will not absorb more salt)
  • citric acid (find in the canning department of the grocery store)
  • 2 9volt batteries
  • alligator clips (2)
  • plastic container
  • copper wire
  • tape, I have used painters tape here, packing tape is good.
My experiment started with 2 containers, one with citric acid, one with just salt water.  I wanted to know if the citric acid made the etch go faster, like in Edinburgh Etch.

I started today with a batch of salt water and saltwater with citric acid (1/2 teaspoon) that had been used once.
notice that the right has copper sediment and the right is just light blue with a few small pieces of copper sediment

Clean metal. Apply your resist (pnp etc)
 Attach a copper wire to the back of the piece with your tape. Cover the entire back and sides with the tape so that your metal doesn't etch away

Use a bare copper sheet (called a sink) and attach to the side of the container.  I just taped it, but a clamp would be great.  Part of the copper (at least  half) should be in the salt water solution.

Hang from a large gauge  (I used 10g) copper wire so that the hanger is in contact with the large wire and the piece to be etched is hanging in the salt solution.

Clip the positive wire to the large wire and the positive side of the battery.

The negative wire to the copper sink and the negative side of the battery. 

The sink will start to bubble.  If it doesn't, check all clips.  If it doesn't bubble it doesn't work!!!

 At 20 minutes I had to clean the sink in the citric acid and I changed both batteries (which were not new, I had etched 1 hr with them the day before) because they weren't bubbling.

I checked the depth of both.  Needed more time.  I shook the plain salt water one to make sure all the copper was not clinging to the piece I wanted to etch.

at 50 minutes I took both out of the water bath, used baking soda to clean and then scrubbed off the resist.

pnp with salt water and citric acid, very clean etch!  depth good

pnp with salt water, look at the etching around the edge, not smooth.  I know its hard to see!

these are the etched pieces. The one on the left is salt water and oil paint. The right side is sharpie with saltwater and citric acid.  Hard to see but the citric side is slightly better etch, smoother and cleaner, not any deeper
Here is a side view of the saltwater bath. Left side has a lot of copper sediment, the right one with citric acid is cleaner...... much cleaner!

For my purposes I will use citric acid, but will use a different power source, one that can plugged in.  For teaching purposes I think 9volt battery will work.




  1. That's a great experiment Debora, thanks for sharing with those great photos!
    This gives me some good ideas for further experiments, too - larger batteries, shorter wire hanger wire, smaller bath containers - I am wondering which of these might help use the electricity more economically.

  2. I know higher volts work faster. not sure if wire makes a difference, but let me know.

    BTW, I used 1/2 teaspoon of citric acid in the bath

  3. Great info Debora! I usually etch electrically with copper sulfate, bit I needed to have something more portable for my teaching. This set-up is great.

    I used a battery pack set-up from Radio Shack that holds 2 D batteries and that works fabulously.

  4. Thank you so much for these detailed instructions! I've been waiting to do electro-etching for a while and bought the battery and clips from Radio Shack, but haven't had the nerve to try it yet. Can you give any advice of the measurements of water and salt you used? And also, how do you safely dispose of the solution afterward?