That URL shows some good stuff on air "sparging". The porous hose
is probably just fine for the job. As you say, the ceramic blocks
(fine bubble version) are probably better but...$$.
I since searched google Australia for diffusers and found lots of
new places dealing with aeration, I must of spelled it wrong in
an earlier search. I found that suppliers to the "aquaculture"
industry have loads of aeration equipment. Everything from 2000+
liter/minute air blowers down to 1 liter/minute small magnetic
diaphragm pumps. In case you want to aerate a small lake of
CuCl2, for example :). There is also "ultra fine bubble
diffusers" that apparently produce bubbles under 0.1 to 0.5mm,
although I don't think we need to go to that level, plus that
would need considerable air pressure (25psi loss).
I am sure that when you get the fine bubbles happening they in a
few hours the etchant will be green. Remember though that the
copper concentration is too high for you to ever see more than
few millimeters into the solution. What you are looking for is
deep green color, or a drop on a white surface will look clear
green. If looking dark drown then there is still some dissolved
copper(I) chloride. I'm not exactly sure how much copper(I)
chloride (or what the state of solution color) can be tolerated
before it starts to effect etching rate. I know that if dark
muddy then its definitely slows down etch.
Adam
grantfair2001 wrote:
> It looks like the Sweetwater air diffusers might be best for the job,
> in that they last forever in an acidic environment, according to the
> manufacturer. There is a Canadian seller but they are on the west
> coast so it will take a while. That firm also sells air diffuser hose,
> which is much cheaper (C$2.00/ft) than the Sweetwater airstone (which
> you pointed out), which is $31 for one 12" stone. Click on 'diffuser
> hose' at:
>
> http://www.direct.ca/dynamicaqua/diffusers.html
>
> It is rubber and polyethylene. Adam, or other group members - any idea
> how that combination would hold up to an acid bath?
>
> In the meantime, on the basis of your experience, Adam, I decided
> against putting pin holes in the hose. Instead I drilled very fine
> holes in an 18" piece of 1/4" ID schedule 40 PVC pipe, plugged one
> end, and stuck the air hose on the other end. The bubbles are finer
> than the sparger makes, but not tiny. Not bad for 1/2 an hour of
> drilling, though.
>
> I have had the sparger on since I removed the mushy airstone. But the
> etchant is still a coca cola brown in color. Condensate (or splash) on
> the inside lid is quite green, though. Anyway, finer bubbles would
> seem to be the key. I will see how the new test aerator does, but I
> think I will at least buy some of the aeration hose.
>
> It's taking longer than I hoped, but when it is ready, I have a lot of
> etchant which will make it easy to etch quickly and keep the etchant
> ready to go - I hope.
>
> Grant
>
>
> --- In Homebrew_PCBs@yahoogroups.com, Adam Seychell
> <adam_seychell@y...> wrote:
>
>>I once tried pin holes in PVC tube, but the bubbles always come
>>out big compared to air stones. I think they air needs to pass
>>through all those small cavities for it to make small bubbles.
>>When experimenting its always a good idea to use a bucket of
>>water first.
>>
>>Adam
>
>
>
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