On 11/11/2010, at 5:41 AM, Philip Pemberton <
ygroups@...> wrote:
> Hi guys,
>
> Does anyone know off-hand what the required ratio of Hydrochloric Acid
> to Peroxide is when starting off a cupric chloride etch bath?
>
>
I personally don't think it's very critical. I started a bath quite a few years ago with simply a small amount (1cm in bottom of tank) of spent ammonium persulphate etchant ( ie it was loaded with copper ) and added about half a tank of hcl. This is one of those fairly common vertical plastic tanks that's about the size of an a4 page of paper. Added copper, heater, bubbler, and it turned green. Don't think it even took that long. So yeah I didn't use peroxide at all. That same tank is still going.
> Do I need to target a specific pH? That is, do I need to buy litmus
> paper and so on too?
>
> What about titration and specific gravity control -- is that necessary?
> I have some sodium hydroxide granules in the cupboard (CIF Photoresist
> Developer; I've been using MEGA CPD5 instead because it's less harmful
> and harder to screw up), but would need to hunt down a suitable
> indicator chemical and glassware...
>
I've never measured gravity or ph of mine. When it's bright clear green it's good to go. Dark brown means it needs bubbling. Eventually you'll get precipitates in bottom (solution's saturated) I just pour off the liquid, clean out the precipitates, and top up with fresh hcl.
Andrew
[Non-text portions of this message have been removed]