Monday, November 10, 2025
Probe Etch Using Salt/HCl
Hydrochloric acid (Spirit of Salts) is easier to get than nitric acid because people don't tend to make explosives from it, and it is widely used in the building industry for removing concrete splat. So I tried using that to prevent the cloudy precipitate when etching a probe and it worked just fine.
I used 40ml of 5% salt solution with 5ml of 0.5% hydrochloric acid to etch a 0.3mm dia. 316 Stainless wire probe as per earlier. The result came out a bit finer than I intended, but I waited for the end of the wire to fall off and it didn't. So, um, less etch time on the next go perhaps?
Anyway, here's the point compared to a 0.5mm hypodermic needle:
I might manage slightly finer detail with that. But as I need the nail gel parts to be at least 30μm thick, this point may be overkill. Still, I've made it so I'll mount it and we'll smash it up once I've got my ducks in a row for the next attempt at layers.
Oh, I definitely need a better USB microscope over the RepRapMicron. It's nigh on impossible to see the resin dots. I might try shaving the end of the housing off this one so I can get it closer to the probe tip.
The image is still quite clear at the scopes max magnification - the only thing stopping it is that it reaches the end of the focus thread. When I need more enlargement I think a bit of hackery extending the case would provide that.
https://www.youtube.com/watch?v=H2P1_JZYnVc
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