Hi Adam -
My etchant continues to slowly progress. It seems that some variable
at this end differs from your approach. Nevertheless, the solution has
slowly changed in the same ways you described.
At present it is a dark coca cola brown, and it is difficult to see
much of the wire under the etchant, although maybe the top inch of
solution is somewhat translucent. Overall, the solution has become
darker and less translucent over time.
I had recently placed a piece of PCB in the solution. It took about 2
days, but all the copper is now gone - so clearly, the etchant is etching.
My tire air compressor failed. It is not meant for continuous duty,
and the conecting rod to the compressor cylinder was what actually
failed, no doubt due to overheat. The compressor directions warned not
to run it over 15 minutes without a 5 minute off period. Since the
pressure was quite low, I hoped that the work done was slight enough
that continuous duty might be ok. Obviously not. The other drawback
with this device was noise. It was extremely noisy. I could hear it
from the basement through two closed doors, and this would have made
it impractical. It did put out lots of air, though.
I finaly got an old Gast vacuum pump going as an air source. I had to
do some work on the motor before it worked. The pump itself has carbon
vanes and they are probably worn, but I suspect that replacement would
be too expensive even if I could find replacements. Meanwhile it has
some bubbles rising through the etchant.
I am hoping that although the process is slow, it will succeed in the
end. I will keep the list posted.
Grant
--- In
Homebrew_PCBs@yahoogroups.com, adam Seychell
<adam_seychell@y...> wrote:
> Grant, I took a 500 ml beaker. Added 20 ml of 8M HCl (20%
> wt) + 20 ml of water and pieces of scrap copper sheet 0.7 mm
> thickness. At this stage about 1/2 of the copper was
> above the liquid level. Over a 54 hour period I measured the
> progress.
>
>
> time HCl Cu mass appearance
> (hours) (Molar) (grams) of solution
> ---------------------------------------------
> 0 4M 12.3g clear
> 12 ? ? pale brown
> 23 ? 10.0 Coca-Cola brown
> -> added 20 ml of 8M HCl + 5 ml water.
> -> started bubbling air through solution.
>
> 23 5.45 10.0 " "
> 34 3.77 3.8 dirty brown liquid
> 46 2.4 0.7 dirty brown liquid
> 54 1.67 0.0 deep green
>
>
> Note: The bubbles were created from a air hose immersed in
> the solution. If an airstone had been used to create smaller
> bubbles then the reaction would of been much faster.
>
> regards,
>
> Adam.