I always like finding new techniques for making and finishing projects, and this one looks to be a hugely beneficial process. Need to get a design onto metal with some permanence? Want to etch your own PCB board designs on copper clad boards? Look no further than the salt-water etching process.
It’s so deceptively simple, it seems like it should be more difficult – but my tests have shown it’s really not. At it’s simplest the process is to make a resist or mask design on the piece of metal you wish to etch – you can do this with paint, tape, permanent marker or toner transfer. Really anything that can adequately cover the surface of the metal where you don’t want it to be etched.
Mix up some ordinary table salt with ordinary tap water until you have a fairly saturated solution. Take a common 9V battery or an AC to DC adapter (you need DC current for this – don’t use a wall-wart that outputs AC, it won’t work and is probably unsafe)
Attach the positive connection from the power source to the project piece, then attach the negative lead either to a piece of sacrificial metal (if using a tank to submerge the whole piece in) or to a Q-tip soaked in the salt water.
If you’re submerging the piece, you’ll need to leave it for a while in the container with the power going. If you are using the q-tip for targeted etching the process can be faster but requires more manual work to rub the q-tip over the areas to be etched. I have found that permanent marker can be worn off by rubbing with salt water so it’s not very good for a resist unless you’re going to go the submerging route.
There really isn’t much more to the technique. The electrochemical reaction caused will eat away at the metal wherever it is exposed. There are some low levels of toxic gasses released so make sure you work in a well ventilated area and avoid directly inhaling the fumes.
For a more detailed tutorial, this one I found for etching Altoids tins that is a very good description of the submerging method. I plan to use this in the next few weeks for my guitar amplifier project and I will try to get some photos along the way to document the process.
If you’re looking to etch a circuit board this way, keep in mind that it is an electrical process so you’ll need to design your PCB with contact points for the positive lead for each copper trace – if your design is complicated you may want to look into strictly chemical processes. I believe that there is a technique that uses vinegar, salt and peroxide to make a low-toxicty chemical etch for copper but I’ve not tried that one yet.
