Re: [EE] home pcb making with HCL + H2O2 by Tobias Wieler .

I think the reputation of of the method is by far worse than the actual risks. Many people make the mistake mixing by far too much of the stuff at a time causing the need to store the used acid for next time. Since the H2O2 will still keep producing gas the mixture cannot be stored in a sealed bottle. Just for my small job today I used 3 milliliters of the acid - so the worst fume emission was getting the small amount out of the 1 liter storage bottle. On all official warning sheets HCL is toxic and corrosive - fully admitted - but I don't believe the rumor of HCL to be carcinogenic. If chlorine was so bad, it would not be used for swimming pool desinfection. The smell I produced years ago when I had to heat up 1 liter or more of acid in my etching-machine every time even for little jobs was by far worse - at least what I remember. Tobias > This is great fun to use ****BUT**** very very very nasty on your > lungs. Said to be highly carcinogenic by some and, even if it's not, a > whiff will tell you that it's not going to encourage your lungs to > last longer. First rate ventilation absolutely mandatory. Failing that > do it outside downwind of anything currently living. By far the best > etchant I've seen, and one of the nastiest.