Etching/marking problems - black just rubs off...why?

A

AndrewC

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Nov 14, 2017
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I've built 2 different homemade etchers, following the "poor-man's etcher" plans on dcknives and then the more sophisticated Chris Crawford design. Both are 12v (I followed the advice in a thread here to do the logiudicecustomknives.com modification of the Crawford design to just 12v as 24 apparently fries stencils). Both have DC for etching and AC for marking.

Using both, I've used the standard SCE-1 electrolyte as well as a saltwater solution. Both give me great etching (DC). Both give me nice marking (AC) with a nice black mark. But as soon as I pull the stencil off, rinse, and wipe - the black goes bye-bye, right away. In previous tests, in fact, without wiping, the black just fades and then rusts (I suspect from what's left and not cleaning it off).

This happens in 80CrV2 (aka 1080+), 52100, and 1084. (I believe I tried O1 as well.)

My suspicions right now have to do with the voltage - should I up it to the 24? - and possibly the electrolyte, although I have the same problem with both. And finally whether I really need to neutralize better with a basic solution rather than just a fast thorough water rinse. Any thoughts?
 
Is the etch there and deep?
What is the power source for the unit?
How is the pad constructed?
 
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That was what I first wrote, but he said the etch was great? My thought is that the power is from a small transformer or the AC is too low..
 
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So: the etching power supply unit I'm using is the Chris Crawford / Bob Warner design, pretty much exactly. It's a 2A, 25.2v CT transformer (and yes I've checked both voltage and current with a multimeter). The electrolyte is (quite fresh) SCE-1 from Electro-Chem Etch / Metal Markings Inc., and I talked to the guy there about suitability for 1080+/80CrV2; he says it's the right stuff.

As to the 'pad': I am using the Q-tip method, but have been diligent about trying a robust matrix of many permutations of wetness, time-of-impression, cooling between passes, making sure there's very good conductivity, etc. - in fact, too much contact time results in a good sizzling sound and a pretty hot surface/stencil/Q-tip, so I know I'm not getting too little conduction.

Since I'm getting good deep etching, when I have it on Etch (DC), doesn't seem I've got a problem there. The problem is simply that I am not getting a good deposit of black when I switch to AC. Just for fun, following your thoughts Adam & Stacy, I switched the leads so that the blade was on red and the electrode was black: no better results. (Given that it's AC that does marking, shouldn't make a difference which is which for AC, no?)

UPDATE, and I think SOLUTION (pun not intended): think I just figured this out! Saw some post about spraying the mark with Windex immediately; think the idea was that the electrolyte itself was eating the black substance (which I'm thinking is most logically Iron (II,III) Oxide, aka magnetite, aka Fe3O4 -- ferric chloride and ferrous chloride don't really make sense). So for fun I tried just a table-salt/water solution, hit it with just AC for a bit, and immediately pulled the stencil off and Windexed the heck out of it. Note that Windex is basic - depending on source authority it's got a pH of about 10.7 - so it's gonna neutralize acids nicely without corroding metal. (Which acid does; base doesn't.) I've got a beautiful, fairly deep-black mark.

I'm sure that now I'm gonna find 300 references to something like "immediately rinse with ______", and do a Homer Simpson "Doh!", but for now I'm doing the happy dance -- and hopefully delivering a major commission, with a beautifully black mark, on time....

Thanks, guys, for the suggestions!
 
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You have to set the black or it will wash away, I've seen windex. I think I've also seen it boiled.
 
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