Homebrew PCBs

Leon Heller wrote:
> ----- Original Message ----- 
> From: "Steve" <alienrelics@...>
> To: <Homebrew_PCBs@yahoogroups.com>
> Sent: Wednesday, May 12, 2004 7:12 PM
> Subject: [Homebrew_PCBs] Re: Blackening copper
> 
>>--- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan
>><stefan_trethan@g...> wrote:
>>
>>>Strange question, i know..
>>>
>>>any ideas how to chemically blacken the copper on a pcb (copper
>>
>>only, not
>>
>>>epoxy).
>>>
>>>For optical purposes, not electric. should be even colored.
>>
>>I found something at an art store a few years ago called "Liver of
>>Sulphur" which I used to blacken copper for antiquing purposes.
>>
>>No idea what was in it, or where I have the bottle now to check. Google.
> 
> As someone else said, it's potassium sulphide. IIRC it's made by heating
> potassium metal and sulphur. This could be dangerous, BTW.

Maybe reacting potassium hydroxide with sulphuric acid could give
something.