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Problems with Power supply and copper etching?

I have been teaching copper etching using salt water and a 6 volt flashlight battery with great success for years now.
I recently purchased this rectifier to use as a power supply from Rio Grande:

Digital 3-Amp Plating Rectifier

Item #: 335201


I thought it would work great and save on disposing of so many batteries.

I thought I could set it to a certain voltage and away you go, but I turn everything up as high as it will go and sometimes it etches and sometimes nothing is happening. The voltage and amps seems to fluctuate on their own?
I am wondering if this was the wrong unit for this application or am I doing something wrong?

Thanks in advance!
Melody Armstrong

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Hello Melody,
I convert cell phone charges that are under 10 Volt and under 1 Amp to use in saltwater and cupric nitrate etching. I have written a book about the process and include how to modify the charger as well as explain why you should not exceed the voltage due to the creation of hydrogen. A slower etch at a lower voltage creates a smoother etched surface as well.
The PDF is $10, you can email me at for more information.


Melody, just curious if you are putting your to be etched piece on the negative side? I’ve been contemplating trying to etch and plate at the same time, using the etch piece to plate my pendant. I’m not sure plate is the right term. I watched a demo of this once and was intrigued by the idea. You have to paint the surfaces you want the copper to layer up on. Then I watched a battery etching YouTube and thought WOW, I wonder if I can do both at once?

Has anyone tried this?

Sarah Budde

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I did try that with a few chargers and never had any luck?

I have the etched piece on the positive side, I have etched for many years, just having issues with the power supply.

Regarding plating at the same time, it will not work because the cathode that attracts the copper does not attach the same way as electroforming for example, it is a film that can be brushed off. The copper molecules that are removed attach to salt molecules and it becomes cupric chloride.

Hi Melody,

We use a 10amp/30volt rectifier in our studio which is typically set to 4 volts to salt water etch. We were having intermittent power problems, the unit would power up, cathode and connections were clean, but the circuit was incomplete. We found that not enough of the plastic sheath had been removed so the lead wires weren’t always making a connection.

It’s my understanding that once the voltage limit is set the voltage and amp reading will then fluctuate depending upon the load required. A lower voltage will take longer, but result in a much cleaner etch.

If you haven’t already, consider calling Rio for tech support. They’re always ready to help!


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Thanks Pam!
I am also wondering if maybe all the salt has been used up in my solution?
I am going to make a fresh batch of saltwater and try again on the weekend.

If you’re filtering the copper salt/solids from your solution to keep it clean there may well not be enough salt. You could try adding more to your current solution before you start over. We’ve been actively using the same solution in classes for months.

There are a couple of etching groups on Facebook that could also prove helpful. Etchers Anonymous is one of them. Mike Moretti has a great tutorial on his website as well.

Hi Melody,

Please give Rio Grande’s technical support department a call at 1.888.225.656 and ask for Thomas. He is our plating expert and will be able to help troubleshoot to see if there is an issue with the rectifier.

We look forward to hearing from you

Phillip Scott
Rio Grande Technical Support

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I use a 2 amp rectifier and have no problems etching with it set at about 1 amp, for a nice, slow and clean etch. If it’s not the salt content, it could be the contact on the back of the piece. Have you considered switching to copper sulphate or copper nitrate as your etching solution? I prefer them as the solution does not need replenishing since the copper ions simply go in and out of solution, and you have no aqueous copper disposal issues. I did find I preferred the etch from the copper nitrate rather than the sulphate, though the sulphate is cheaper and you can buy it as root kill.

I’m not an etching expert, but everytime I etch with the same unit you have, I take some sand paper and sand the negative side of copper so it is cleaned off and not dull. Not sure if there is and oxide build up. My rectifier is usually set around 1.5-1.7 volts.

Thanks Kenneth
I will try this next time I etch.

Thanks Dana!