Etching Holes ...

[Ian A. Vine phone UK 0171 419 3450]

>I question whether the acid would eat straight down and not sideways.
>Acids like edges. (You can even sharpen files with Nitric acid.)

Yep, this is correct. The acid will eat at an angle from the exposed
section under cutting the masked off portion. I think the angle varies
depending on the material being etched, etchant, temperature and probably
a whole load of other things. It is usually refered to as the etch factor 
but what the number means I don't know

Ian

Ian A. Vine     | email i/p     iav at hep.ucl.ac.uk
                |       decnet  uclva::iav