Homebrew PCBs

David Cureton wrote:
> 
> By your own admission "I just don't know one chemical from another" I 
> would strongly recommend using the commercially
> available etchant as they are not _that_ expensive. Mixing you own 
> etchants involve using chemicals that are quite dangerous
> if not handled properly.  

Depends what your making. If you decide to make some ammonium persulfate 
then it doesn't require or use dangerous chemicals at all, just boring 
old ammonium sulfate, the stuff for fertilizing your garden.


For example, are you aware you should never
> add water to acid. ALWAYS add acid to water!  Once you
> have the etchant there is more chemistry in correctly maintaining it.

Don't have to be acid. Every tried adding about equal parts warm water 
to sodium hydroxide ?   :)

Once I added a pinch of 99% sodium hydroxide to a few drops of 99% 
sulfuric acid. I wanted to see what happens when pure strong acid comes 
in contact with a pure strong base. Standing about 5 meters away when 
the NaOH the crystals were added they initially just floated without any 
reaction. About 10 seconds later the violent exothermic reaction 
started, giving cracking sounds which almost seemed to break the glass 
beaker. Most of the NaOH was blown away, but what did react caused a 
thick sulfuric acid mist to rise from the beaker and lingered for 
several minutes around the room.

Adam