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.