Hello there, this is my first post so I hope that some one can learn something from what I am about to share.
DISCLAIMER / WARNING : I'll start with this right off because I don't want anyone to get hurt. Strong acids and electricity are dangerous. So be very careful and use proper safety measures, also don't attempt to do anything that is outside the limits of your ability.
Well this is certainly not new info, youtube is littered with videos of the concepts that I am about share. What I will present in the instructable is the results of several experiments that I did.
Here we go... the first thing that you need is a knife blade or whatever metal object that you wish to etch. Once you have the blade you must clean it. To do this the first thing I did was polish it and the washed it with acetone. There are many ways to do any given step in the instructable, the ways that I tried are not the only ones that exist.
Next step is to cover the blade with something that you cut / scrap away to make the pattern. I used a mixture of beeswax and asphaltum powder (which can be purchase at art supply shops). Other coating include electrical tape or nail polish. To make the beeswax mix first melt the wax and then stir in the asphaltum... then allow this to cool until hard. Heat the blade gently until it melts the wax mix; rub the wax on the heated blade as evenly as possible.
Now you are ready to cut / scratch your design into the wax. If you are using electrical tape an exacto knife is probably the best tool to use for your pattern. I used a simple steel scraper that looks like a large tooth pick... you could use a regular tooth pick if you want though I am sure you will go through several of them, as they will get dull quickly. The sky is the limit to what you can do here in terms of artistic design. The only thing to remember is to let the wax cool all the way first. Then to warm it up ever so slightly by holding under a light or in the sun for a minute of two before you begin scraping
Ok now to add a little spark to the process. I tried 3 acids and 3 different voltages.
Acid: vinegar and salt / hydrochloric acid / phosphoric acid
The positive terminal is attached to the blade and the negative terminal is attach to (in my case) a q-tip that has been dipped in acid. All you do then is rub the q-tip around the design until the desired depth of etch is achieved.
I first tried 4 AA batteries which supply a voltage of about 6 i think... And i got reasonable good results with the vinegar mix and better results with hydrochloric. The phosphoric acid hardly did anything so I stopped using it after that.
I then switch out the AA batteries for a car trickle charger, and set it to 6 amps and 6 volts. The results improved as you might expect with the hydrochloric out performing the vinegar.
At this point just the heck of it I turn the charger up to 12 volts at 6 amps and tried the hydrochloric acid again. This time the q-tip melted and I could hear the very distinct hum of electrical current.
Once you have reached the desired depth of etch, all that is left to do is clean off whatever you used to draw your design in (be it wax, tape or whatever) and polish the blade.
I would like to say that if you are just doing this once in a while AA batteries and vinegar will achieve an etch that looks good and the you can feel when you run your finger over it. I went to all this trouble to find a better way. Which I did find... using 12 volts and 6 amps and hydrochloric acid I was able the achieve a deep etch in less than a minute, while the batteries and vinegar took several minutes and was not quite as deep.
In the picture the braided pattern was done with vinegar and 6 volts and 6 amps and the butter fly was done with hydrochloric and 12 volts and 6 amps.
Not very much new info here but I tried to take a simple approach to the next level... Thank you for reading hope that this helps