Re: gEDA-user: PCM making methods - was - Re: alarm clock update

[John Griessen <john@xxxxxxxxxxxxxx>]

>> Daniel Sandström wrote:
> 
>>> http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/index.html
>> The first one only contains B&W pictures, so the second one is much
>> better, as color matters :)

from etching_CuCl/index.html:
the solution effectively just grows as it consumes four ingredients during its lifetime.
These include; copper metal, oxygen (from air), hydrochloric acid, and water. The
overall equation during regeneration can be written as;

[4]     2HCl {aq} + 2CuCl {aq} + O {aq} →  2CuCl2 {aq}  + H2O{aq}

So this solution does grow some from balancing by adding acid,
and by H2o production during regeneration...   The disposal methods are
going to be the same as with H2O2...neutralize excess, sell
the copper oxide sediment.


Hmm....  "recommend optimum specific gravity to be between 1.240 to 1.330"

I wonder if the wine gravity gauge I have has that range....

Here's a big consideration:  "graph demonstrates that when more than approximately
5 g/l of copper is dissolved in solution and is not regenerated, the etch rate
begins to decrease, and becomes almost zero when monovalent copper reaches 20g/l."

That means bubbling as you go, or all stop...   The write up shows a photo that is
about like you get in phases of a H2O2 bath (with no titration required -- all the time)
http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/cucl_colors2.jpg
is the range of colors of a H2O2 bath, yellow green being lots of H2O2, close to too much
where HCl bubbles out (undesirable -- avoid that).   The write up says dark green is still
good for fast etching, so waiting till blackish green is OK, then add H2O2 until mid green will
avoid fuming.

H2O2 is a valuable aid to the method of making a bath.  I found the high strength kind (35%) at
a hydroponics supply place of all things...at a good price of US$ 9 per liter made by Grotek
in Canada.

John Griessen
-- 
Ecosensory   Austin TX
1


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