Homebrew PCBs

Thanks for the additional information. Did you use the pipe layout
which Think and Tinker recommends, like a U shape, with the PCB in the
middle between the "legs" (if that makes any sense at all)?

The air tubing I have on hand is Tygon F-4040 A. I know little about
it except it's cheap at my local surplus store and I believe it is
fairly non-reactive to most chemicals. (Please correct me if I am wrong.)

For air I thought I would try a portable tire inflator from Harbor
Freight, or perhaps an old Gast vacuum pump I've had kicking around
for years, if I can figure out how to use it as a compressor. Failing
that a buddy has offered an aquarium pump but my etch tank is a 34
quart capacity Coleman chest cooler, so I am unsure it will have the
needed air volume.

I have also found some cheap 1/2 mL pipettes (C$ .25) and a surplus
100 ml cylinder specified to +/- 1 ml (C$ 7), which seems like it
would be fine for measuring for titration, since the article suggests
results within  +/- 10% are fine for adjusting the acid level. I am
hoping a student burette will do the trick since, so far the best
proice for a legit version will set me back $140 Can. 

Also- anyone know of a reasonably priced source of bromophenol blue?
So far the best I have seen is C$ 65.00 for 5 grams of ACS grade. That
seems like an awful high price, and if a lab grade is available I
assume that would work ok.

Grant

--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell
<adam_seychell@y...> wrote:
> That's good you found a place selling that stuff, sometimes these 
> plastics are hard to locate. Stay with PVC , because its the only 
> plastic you can easily glue and bend with a hot air.
> 
> I've built several air spargers systems over years for aerating 
> tanks. The 1 mm diameter holes in PVC ridged pipe works ok if you 
> got a big air supply. It gives you large bubbles and they can 
> tend to flow into a stream on one side of the tank. Its more 
> effective to have lots of fine bubbles, as the liquid/air surface 
> area is increased and tends to produce more uniform sparging. I 
> use some porous garden irrigation hose. Its usually available in 
> say 20 meter rolls with a 12 mm ID. The remaining 19.5 meters can 
> be used on a garden :).
> 
> DIY irrigation supplies also make good places to buy chemical 
> resistant plumbing. Be careful, some fittings are made from nylon 
> and won't last in HCl. Burn a small part of the plastic and it if 
> bubbles and fizzles and the smoke is very irritating then its 
> nylon. If the plastic simply melts when burning and maybe even 
> drips on the ground then you have polypropylene fittings. 
> Polyethylene burns similar to polypropylene except the smoke 
> smells like candle wax smoke.
> 
> The more air the better, so buy the largest aquarium air pump you 
>   can afford. I though of using a sewerage treatment aeration 
> pump, but they are $$$.