I need to etch holes in a glass substrate (lead glass), the thickness of
which are between 0.5mm and 3.0mm. I was told that I should be able to
achieve an aspect ratio (hole diameter to substrate thickness) of about
100:1. I am looking for through-hole sizes about 50 microns in diameter (at
least on the surface). Etching could be carried out from both sides of the
glass. Can anybody please offer me any information on the correct acids
(solvents for lead glass only), temperatures, times etc,etc,etc.....

Also, does anybody know where I might be able to procure glass capilliary
tubes with inside diameters in the range of 20