Homebrew PCBs

Andrew wrote:
> 
> 
>  > Lots of people wrote:
>  >
>  > ...ABOUT SODIUM CARBONATE
> 
> Does this dry film resist people are
> playing with not develop under sodium
> silicate?
Correct.
> 
> The pre-sensitised boards I use prefer
> sodium silicate over other developing
> chemicals.

Is that a 'positive' (exposed areas wash away in developer) resit ?

The negative dry film resist must be developed in Na2CO3 and should be 
%0.9 to %1.1 concentration, at 25 to 35 deg C. Interesting, high 
concentrations (>%10) actually slow down the development process.
The very high pH of sodium silicate will strip negative film right off 
the board. You use NaOH at %1~%10 to strip it off board.