Homebrew PCBs

Earl T. Hackett, Jr. wrote:
> 
> The addition of any additional salt content, either sodium or calcium, can 
> be a problem.  I'd have to dig way back to get the details, but in general, 
> its a good policy to avoid adding stuff to a chemical system if it can be 
> avoided.  There are side reactions that can be really bad news - like 
> hydrogen gas generation that can cause big BOOMS.
> 

I agree. Its best to keep the chemistry simple, and air is not something 
that you can add too much of. I found that air regeneration of CuCl 
depends greatly on bubble size. The finer the bubbles the faster the 
regeneration. If the bubbles are extra fine then the regeneration rate 
is fast enough to cause noticeable heating. A 1 or 2 inch layer of 
foaming on top of the etchant makes it work very fast , in one or two 
hours or so compared to several days.  If anyone is getting problems 
with HCl fumes then they have too much acid. Air generated CuCl etches 
ok with almost zero acid. The important thing is to keep the tank 
relatively sealed because of mist produced from bursting bubbles will 
eventually cover everything in the surrounding area with microscopic 
droplets of etchant.