Spontaneous Etcher

Spontaneous Projects is a chronicle of all of my projects, a reference for me, and a way to prevent others from making the same mistakes.

Hole through a hatchet, masked with packing tape

Last night I was out with a friend, a bladesmith based out of Canberra, and he was discussing the need to place makers marks on blades to make a name for himself, which is easy enough on a fully forged blade using some punches when the blade is malleable. 
He's looking into doing a few cheaper blades, just ground down, so the risks of bending it, and the time consumed make punching inefficient. 

He mentioned Electroetching, using a DC current and some salt water, to remove iron ions from the blade, removing material and resulting in an etched blade. He's done a proof of concept before using a few 9v batteries, but felt that it was too dangerous, given how the batteries heated up. 

 I have a few old laptop chargers lying around, including a 19v, 4.67 A charger, that is unlikely to be all that useful for powering other things. 
So today we made up a new etcher, and tested it on a few blades; an old machete, a stainless cooking knife and a hatchet. 

By masking the area with nail polish, and scratching a design through the polish it is possible to create the design. The remaining area of the blade was protected with packing tape, while the positive electrode was clipped to the blade, and the negative attached to a ball of cotton wool soaked in a mixture of vinegar and salt.

The first design (left) was just a wordmark "Bruce !!!", and worked quite well in about 5 minutes with a heavily salted solution. However the area that was masked with polish was also etched slightly, due to uneven, or insufficient coverage. 

Emboldened we went for a more complex design, the bearded guy below, this was less successful, as the cotton ball had to be moved around to ensure good coverage, and the polish lifted in places. 



We decided to see what shape the process created below the surface with a deeper etch, and how long it would take, so a rectangle was masked out with tape, and a hole made through the machete - minimal heating of the power supply, despite working for over an hour to get through ~2mm of material in a 12x3mm rectangle. This required several cotton balls, a lot of electrolyte solution and a bit of movement to clean out the etched area occasionally. Not something that we'll want to do to blades, but a good proof of concept.

Wanting to make something a bit more practical, and test the process on a different material we tried a hatchet, cleaned up the rust a little, sanded it back, and made a design that will likely be similar to his final one, a Celtic knot, and his initials.

The photo doesn't show a lot of detail here, but the etching wasn't particularly smooth, possibly due to the design in the polish, or too aggressive a process, but it etched, and gave a recognisable mark.

The last thing to test was the behaviour of stainless steel, so a kitchen knife was etched, again the polish layer was a little thin, and we started off with no salt in the solution, but it was too slow.   Increasing the salt content increased the reaction rate, but it was still slower than the steel blades.

End result was promising, but we need to find a better way to mask consistently.

Thoughts:

• Masking needs to be waterproof and possess high resistance
• Masking needs to be held tight to the material
• Timing is important, and will vary for different materials
• A new switch is needed, and a new clamping method is desirable

Ideal masking will be plastic film, cut to shape in bulk, so either a sticker manufacturer, or one of the stamps that you can get at lincraft etc.