Examining the manufacturer recommendations ( both Cramolin and Kontakt Chemie photo resists) we get this:- 200 ml hydrochloric acid (HCl 35%) 30ml hydrogen peroxide (H2O2 30%) 770 ml water This is to make up 1 liter Since drugstore peroxide ('40 volume') is about 12%, one needs about 90 ml. This is rather convenient, as the formula works out close enough to a simple, easy 1, 2, 3.....1 part peroxide, 2 parts acid, 3 parts water Hydrochloric acid is also known as 'muratic acid' or 'spirits of salts' in a hardware store, but 5 liters of pool acid is a lot cheaper. There is a possibility, although remote, that organic material might ignite spontaneously if it came into contact with the mixture where the water has evaporated off. In practice, the solution is quite safe, and can be flushed away, since it breaks down into more or less harmless stuff On Thu, Jun 6, 2013 at 12:28 AM, Allen Mulvey wrote: > I use one part Muriatic Acid (cheap hydrochloric acid) from > Ace and two parts drugstore variety hydrogen peroxide. It > works extremely well. I only do small "hobby" jobs so > everything is rinsed down the drain when I'm finished. > > Allen > > > -----Original Message----- > > From: piclist-bounces@mit.edu [mailto:piclist- > > bounces@mit.edu] On Behalf Of Marcel Duchamp > > Sent: Wednesday, June 05, 2013 5:09 PM > > To: Microcontroller discussion list - Public. > > Subject: Re: [EE] differences between ferric chloride and > > sodium metasilicate PCB etchants? > > > > On 6/5/2013 1:47 PM, Perry Curling-Hope wrote: > > > Fastest, cleanest etching 'cut' is accomplished with > (Hydro) > > perchloric > > > acid. > > > This is dirt cheap and readily available, produced by > mixing > > pool acid > > > (HCl,, hydrochloric acid) with hydrogen peroxide, the so > > called '40 volume' > > > (12% H2O2, used as hair bleach and a > disinfectant/cleaner > > which is > > > available from a drug store) in appropriate proportions. > > > > What are the "appropriate proportions"? > > > > > Results have been so outstanding, I have not bothered > > with anything else. > > > Perchloric acid is quite safe to work with at these > dilutions. > > Which dilutions? > > > > > Do not leave the etching tray to dry out...dispose > > immediately after use > > > > > What happens if the tray dries out? > > What is the appropriate method of disposal? > > > > Thanks! > > -- > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list > > archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 Perry Curling-Hope Research and Development --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .