Homebrew PCBs

Phil wrote:

> What it boils down is that there are lots of ways of getting the same
> result with relatively the same level of efficiency.

yep, and each of us has a preferred choice on what system to use.


> One other thing I haven't seen discussed is the effect of etching
> speed on pinholing with TT.  I think (though have no way to prove it)
> that pinholing is proportional to etch time.  It seems to work out
> that way.  The last batch (the one I mentioned) had almost no
> pinholing at all.  I was very pleased with the result.  Even under the
> microscope, it looked suprisingly clean for TT.   
> 

As I understand the "pinholes" are just small voids in the toner coating 
the copper. How can this effect etching rate , which is governed by a 
chemical reaction ?