RepRap: Blog

Probe 9 was given a pitted surface by etching in dilute nitric acid. This allowed more resin to cling to the body of the probe, but nitric acid is restricted in many localities due to its use in illicit explosives manufacture. It gives a particularly pitted surface because it is a powerful oxidizing agent. So, I pondered on what commonly available oxidizers are in use that haven't been restricted yet. Ordinary household bleach sounded like a good starting point, it also being a starting material for a number of energetic compounds. The stuff under my kitchen sink is 42g/litre which works out at about 4%. I'd have preferred something stronger but hey. Etching as before with a 10mm immersed 316 stainless wire gives this at the tip of Probe 11:

Comparing with the wire etched in acidified 5% sodium chloride to make Probe 10, we can see that there is a promising amount of pitting (sorry, couldn't remember the magnification I used and this is about twice the magnification of the previous image):

Worth exploring further. Caution: Do not add hydrochloric acid to the sodium hypochlorite. This will immediately generate chlorine gas. Probably not in lethal amounts in the quantities I'm using, but I recommend against empirical experimentation in that direction.

Next I'll experiment with getting a regular, smooth, pointy tip.