Electro-Etching

Etching patterns (not damascus) into blades/other things has long been on my list of things to try, and I finally found a moment to give it a try with mixed success. The basic process can be done a number of ways, all involving an etchant and a resist. The resist marks where the pattern will be by leaving the steel bare wherever you want to achieve depth. Everywhere else is then covered with something, ranging from vinyl stencils, toner, wax, and in this case, electrical tape. For the etchant, I used salt water and electricity.

First, I had to find something to etch. I decided it was the perfect opportunity for a blade that broke before tempering that was once destined to become a new design for a kitchen knife. After a little (a lot) or re-profiling, I came out with a passable straight razor of an atypical shape, due to the previous proportions.

I left the surface rough, around 220 grit from the belt sander. I find that the tape adheres better to a rougher surface, and the etch takes better. Covering the entire face to be etched with hardware store variety electrical tape, I proceeded to sketch a thorny knotwork pattern onto it and cut it as carefully as possible with an xacto knife. The above is the result of the first step. It is not much, more for proof of concept than anything else.


Next, I went to the recycling and pulled a bottle, cut the top off, and filled it with salt and water. Mix in the salt until it does not dissolve any more, and then add a little more. Heating it helps the process somewhat. I then gathered the remainder of my materials. At this point, I had
-Salt water
-Q-tips
-12 Volt Battery charger
-Towels

As shown above, the red (+) lead of the battery charger is clamped to the blade, and the black (-) lead is holding a salt water soaked Q-tip.

I will take a moment to talk about the battery charger. This was the biggest unknown for what I was doing. Before trying to find one, I was not entirely certain what it would look like or where I would find one. Oddly enough, they were with the 12v batteries. Specifically, the car batteries and the like for other motor operations like dirt bikes, motorcycles, and large toys. There were quite a few to choose from, and this happened to be the cheapest (at my local big box store). I would not recommend anything with automatic shutoff or 'intelligent' auto selection of voltage/current. They simply do not work as well, as the thing you are 'charging' is not a battery. Those safety precautions designed to prevent people from electrocuting themselves or burning out the starters causes it to be less effective when completing the circuit with a piece of steel. Shorting it, actually.

When it comes time to actually etch the piece, clamp the wet q-tip in the black lead and touch it to the exposed metal. Do NOT touch the lead itself to the metal, as it will spark and short and likely cause some sort of electrical fire. It is not that difficult to avoid.

Almost immediately, the salt water will begin to bubble and turn to steam, leaving the steel dark and discoloured with a slime around the tape. That is not caused by the tape melting or burning, simply part of the process. However, I would advise against breathing it in if all possible and doing this somewhere with good ventilation.

It is important to be as uniform as possible in where you contact the metal. For larger designs, always keep the q-tip moving. Re-wet as often as necessary; dry, it will not do anything. The salt water carries the current to the steel and when electrified is quite corrosive.

You may come to the point that nothing happens any longer. That is likely because either you need to use a new q-tip or just wipe off the surface of the pattern. Be careful, as it may lift the resist. I was able to run it under the kitchen sink to clean it with no issues.

The depth and detail of the pattern is determined by the amount of time you etch it. For this experiment, I etched it for a total of around 15 minutes, spreading it as evenly as possible over the entire pattern.

Then simply peel off the resist, and there is the pattern. I had tangible depth to this, which was the idea, as I still have to sand the blade and finish it. A few observations. First, the line where the blade hardened and did not was very distinct in that the softer metal was brighter. In the picture, you can almost see it in the leftmost part. In person, it is almost white. Second, the lines where the layers of tape overlap will create a small etch line that needs to be ground out. Similarly, where the pieces of tape (if you are using that) that are not held too strongly will try and lift off the steel. Just be careful not to drag the q-tip into the ends of the tape, but rather with them so you are not pushing on them.

I will continue to experiment with depth and uniformity of the etch, as well as post-etch finishing of the relief. More updates to come soon perhaps.