30 vol is 3%.
the vol indication is about how much O2 is produced from the product.
3% has water enough, don't need to add more.
what runs out is the O2 produced. you can regenerate it either with more H2O2 (more water) or with bubbling air.
the etchant will last (almost) for ever. if you leave it open, some of the water will evaporate (thats good)...
--- On Thu, 3/18/10, mlerman@... <mlerman@...> wrote:
>
> Ah, it does say 30 vol - I assumed that was 30% by volume
> (I'm not by any means a chemist). Please educate me as to
> the difference and what it implies for my usage!