Homebrew PCBs

This pretty closly matches my experiance. But I saved mine, and set 
up a bubbler to regenerate it.

After I used it for the first couple boards, I bubbled for a couple 
days, and it turned back to a bright emerald color. It looked like I 
wasn't going to need it for a couple weeks, so I turned off the 
bubbler. When I came back to it it was noticably darker and took 
forever (45 mins to an hour) to etch.

Since other people had said that it would regenerate without a 
bubbler (given lots of time) I didn't understand why it de-generated. 
(still don't)

Confused, I decided to conduct some experiments: First I ran the 
bubbler for 24 hours. The color returned to bright green and a small 
board etched in about 10 minutes. I tried to etch a second board the 
next day (about 16 hours) and it was back to taking forever. 

Based on that I figured I should bubble imediatly prior to etching. 
The next week, when I needed another board, I hooked up the bubbler, 
and ran it overnight. Next day I tossed in my board and waited. The 
proccess started pretty good, but seemed to get slower and slower, 
and the solution darkened significantly before the board was done. 
The board wasn't any larger than anything else I'd done (about 4x5 
inches) Eventualy in an attempt to save that board I put the bubbler 
into the tank with the board. I was able to save the board, but total 
time was probably about 2 hours, far cry from the 5-10 minutes when I 
first mixed it up.

I've been planning to build a new board holder that has a bubbler 
built in, but I would realy like to understand my etchant better.

Even with the problems, it's better than ferric chloride.

BTW, the idea of neutralizing the acid before poring it down the 
drain- realy kinda pointless. The acid is no worse than lots of 
toilet cleaners and drain cleaners. In fact when I was a kid we lived 
in a house with a well and REALY hard water. About once a month my 
dad would use strait muratic acid to clean the toilets.

The part that's considered toxic is the excess copper in solution, 
which isn't neutralized by the baking soda.

-Denny

--- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan 
<stefan_trethan@g...> wrote:
> Nice to hear you have good results too.
> What i notice is that with a older etchant it takes longer and 
longer.
> i do not know what is amiss but my solution hits the one hour mark 
now 
> with
> little enough peroxide not to make clor gas.
> 
> Was much faster in the past, i would like to have it that fast 
again.
> Any ideas anyone?
> I make a pcb about once a week so i would not like to discard it....
> 
> ST
> 
> 
> On Fri, 13 Feb 2004 05:13:03 -0000, klmjr22 <keithlmartin@c...> 
> wrote:
> 
> > Just thought I would describe my experince using muratic acid and
> > peroxide to etch a couple of boards. I used a plastic shoebox the 
semi
> > white flexible kind poured in 1 cup 3% peroxide and 1/2 cup 32%
> > muratic acid (swimming pool type) added slowly. the acid was 
about 40
> > degrees as I store it outside. no fumes or bubbling was noticed 
during
> > this time. The liquid was clear. Put in the board which was 
covered
> > with riston dry resist and touched up with a sharpee. the exposed
> > copper immediatly turned dark reddish brown and the solution 
turned
> > emerald green in about a minute. Very pretty and quite clear. The
> > board was 6" by 3 1/2" it was totally etched in less than 5 
minutes. I
> > used a gentle rocking motion. At no time did any noticable fumes 
come
> > off the process. About 20 minutes later I started etching another
> > board about the same size. When I started I noticed many bubbles 
had
> > appeared on the bottom of the shoebox. the board etched much more
> > slowly. I added about 1/2 cup peroxide and it sped right back up. 
When
> > the second board was complete I neutralized the acid by slowly 
adding
> > backing soda. when the fizzing stopped I diluted what was left and
> > poured it down the drain. I realize it can be regenerated over and
> > over but due to the small amount needed to etch the board and the 
fact
> > I am very interrmittent in my etching needs making small amounts 
fresh
> > seems like the thing to do. I believe what I ended up with was the
> > cupric etching solution and if so it is MUCH faster starting with
> > peroxide insted of bubbling for a week to get it started.
> >