Homebrew PCBs

Russell Shaw wrote:

> Leon Heller wrote:
> 
>>----- Original Message ----- 
>>From: "Russell Shaw" <rjshaw@...>
>>To: <Homebrew_PCBs@yahoogroups.com>
>>Sent: Saturday, May 15, 2004 8:10 AM
>>Subject: Re: [Homebrew_PCBs] Re: Blackening copper
>>
>>
>>>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.
>>
>>That will give potassium sulphate, not the sulphide.
> 
> 
> Thought so. But isn't there a heating/reducing step to turn it
> into sulphide?

I know when you *really* heat salts you will get most stable 
form, which would be potassium oxide.