HI,
        Alternating layers of Cr (which sticks well to glass) Au and the
Cr again seems to work well. Depending how long you etch you can go
thicker or thinner, Cr might be enough by itself. It protects well, but
not without pinholing if the layer is too thin. 1000 angstroms Cr should
be good for etch depths of about 40 microns. For etch depths around a few
microns 100-200A is good enough.

Ziggy