Homebrew PCBs

ghidera2000 wrote:
> Well, after babbling away about how good my el-cheapo ML-1210 laser 
> printer makes transparancies, I made a little board (4"x4") with 
> 0.008" traces on 0.020" centers over half of it and the other half 
> as a ground plane. The transparancy came out great, no pinholes etc. 
> Exposured and developed, only found one small break (and a 
> corresponding piece of dust on the transparancy). Quick jab with my 
> sharpy and its ready to go.
> 
> The shocker was when I went to turn on the heater for my ferric 
> chloride. I hadn't realized it but its been months since I etched a 
> board - instead of being a translucent dark brown, it was an opaque 
> greenish brown goop! I didn't have any more on hand and it was a 
> sunday so..., topped it up with water, heated it up, and etched 
> anyway - worked perfect! In fact, this was about the best etching 
> I've managed (probably because I exposed longer than needed and got 
> more aggressive with brushing in the developer.
> 
> Why would it turn green? Something growing in there?

The active ingredients can settle to the bottom. Add some HCl and
stir it.