The dangers of over etching

**rlobrecht** · 01-03-2017, 10:05 AM

Although not quite Star Wars or lightsaber related, the lessons learned still apply.

I have two Starbucks brand steel insulated coffee cups. They are 16 oz, and are straight cylinders. Despite washing them by hand, the paint started chipping. This past fall they got to the point where they looked pretty bad, so I decided to strip all the paint, and etch designs into them. After a little Google-fu, I found that the techniques in ARKM's tutorial should work on stainless steel.

I fired up my wife's Cricut machine to make some stencils, and used packing tape for the remainder of the resist. I didn't have a long steel bar for the negative side, so I used a straightened staple. It ended up being about 5" long.

The etching seemed to work fine. I got bubbles, and the water turned really gross. So gross, that I couldn't really see the progress. After about 9 minutes, I decided I had waited long enough. I pulled the first cup out of the mix, and rinsed it off. All the areas seemed to be etched, so I pulled off the resist. I found that it was etched, but not as much as I wanted, and the back side didn't get etched much at all. I remembered that the most etching would be on the face close to the negative pole, so for the second cup, I decided I needed to leave it in longer, and turn it so the different faces faced the negative pole. Since I was leaving it longer and turning it, I went from 9 minutes to 27 minutes, and I rotated the cup a little every few minutes.

At the end, I pulled the cup, and water came pouring out of one side, I got a nice deep etch this time, but in a few spots, the etch was too deep and etched completely through.

Looking back, I should have been checking it a little more carefully by rinsing it part way through.

From my recollection, aluminum etched faster, so I could see the same thing happening when etching a saber body.

Lessons learned:
-the face of the part closest to the negative lead etches the fastest
-you can etch completely through the part

**darth_chasm** · 01-03-2017, 10:44 AM

One way to get around having to keep turning the piece to face the cathode is to use heavy gauge wire of the appropriate metal and coil it around the ID of your container.

Just got the Cricut Explore Air btw. Haven't etched yet, but I'm pretty pleased with the cut.

**jbkuma** · 01-03-2017, 11:25 AM

I've debated doing this on purpose to clear out some material. I know it wouldn't be perfectly clean, but it could save a lot of manual work by, if nothing else, thinning the bulk and giving an edge to work to.

**ARKM** · 01-03-2017, 12:04 PM

rlobrecht, sorry to hear it. I've had that happen with brass sink tube before. It sucks.

darth_chasm, I don't think that wrapping the wire around the inside of the container is a good idea. I have tried using three rods for the cathodes, in a triangular fashion, all split from the same point on the main wire with an equal amount of wire leading to each rod. This did not help the etching process and caused the battery charger to trip it's internal, automatically resetting breaker, more often. I'm guessing that this has to do with the flow of electrons. They "prefer" moving in straight lines. I have also tried two rods with similar results. One 1/8" dia. rod has always worked best in all my tests. However if there is etching do be done all the way around the piece, I do rotate the piece every so often.

**darth_chasm** · 01-03-2017, 12:57 PM

Interesting. I admittedly have not done it with etching yet, but it is the same set-up I use for plating to get a fairly even plate on all sides and it works very well. Have not run into any electrical issues. I use a bench power supply. Don't know if that makes any difference.

I'm a rebel, so I think I'll try it out when I'm ready to etch to see what happens. If I blow up the apartment I'll blame it on faulty gas lines.

**Greenie** · 01-03-2017, 12:59 PM

I find rotating the work piece at regular intervals usually works well. I submerge in a large coffee jar but Im wondering now if a metal container could be used connected directly as the negative (?)

**jbkuma** · 01-03-2017, 01:23 PM

I read a post once that suggested a cheap pot could be used if you had a good way of suspending the work piece. That was before I discovered there was actually a saber smithing community, and many of the things I was editing lexperimenting with were old hat.

**ARobb73** · 01-03-2017, 02:26 PM

Originally Posted by jbkuma

I've debated doing this on purpose to clear out some material. I know it wouldn't be perfectly clean, but it could save a lot of manual work by, if nothing else, thinning the bulk and giving an edge to work to.

I did this to randomly simulate blaster damage on a saber, then covered it with a sink tube shroud to make it look like a 'quick' in the field fix. The random munching of the non-resisted metal really made it look pretty neat.