Design, Build, Test, Iterate

DIY PCB Etching: Safety Lessons Learned

I wondered for a while about the title of this post, because I have actually learned very little in terms of safety. After all this, I know I’m still not going to use a fume hood, I’m still going to do this in my garage (albeit closer to the door), and I still won’t wear goggles even though I have a pair hanging on the wall three feet from me.

I do know, however, some things I shouldn’t touch with bare hands anymore. I can deal with latex gloves. Do as I say, not as I do. Be safe.

Chemical burns do not necessarily hurt immediately, even after an hour or two. Even though you may feel nothing, the damage may have already been done.

Mild caustic burns on my leg a month ago.

Mild caustic burns on my leg a month ago.

Sodium hydroxide on skin produces many, many itchy blisters crowding the entire affected surface that become painful and oozy when popped. I’m guessing the ooze is probably due to cells producing fluid to help dilute the hydroxide ions. The blisters itch worse when wet.

What I don’t understand is how I got the stuff all over my limbs and face. The only way I can imagine that happening is by having some on my fingertips and scratching myself with said fingertips, but my fingertips are perfectly fine.

It couldn’t have been the hydrogen chloride or chlorine gases, because the burns were not uniform. That said, in addition to the large patches and streaks of blisters, I did get small, less-painful-but-just-as-itchy blisters fairly evenly peppered across the shins of my legs, on my forearms, and the backs of my hands.

Corrosive gases in the throat produce a lasting, scratchy, stinging sensation. Even on the cathode side, the popping bubbles can release a mist of sodium hydroxide into the air that can be breathed in. Cover it up with tissue paper (or do it under a hood like you’re supposed to), and don’t breathe too near it.

Temporary hydrogen peroxide "burn" on finger.

Temporary hydrogen peroxide "burn" on finger.

Concentrated hydrogen peroxide leaves a stinging, temporary white “burn” like the one pictured above. I didn’t notice it until it started hurting madly (feels just like having antiseptic in an open wound; go figure), and the whiteness might be due to many small bubbles formed just underneath the skin. fortunately, the bubbles dissolved back into fluids in the finger and the burn disappeared.

Finally, after four weeks, all of the small blisters from the gases have disappeared. Unfortunately, the larger burns from the hydroxide left behind darker patches of scar tissue, and some still have a central, scabby hole in the skin where the main blister used to be. At least nothing itches anymore.

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