Try Aqua Regia. The composition is HCl: HNO3:H20 = 3:1:4

> ----------
> From:         Andrew CAMPITELLI[SMTP:campi@lpmo.univ-fcomte.fr]
> Reply To:     Andrew CAMPITELLI;mems-cc@ISI.EDU
> Sent:         Monday, February 16, 1998 10:54 PM
> To:   MEMS@ISI.EDU
> Subject:      transparent Au etchant...
>
> Dear Colleagues,
> I am searching for a supplier for a gold etchant that is transparent
> (clear).
> We are currently using a KI solution, which works well but has the major
> disadvantage of being non-transparent.
> Any suggestions would be greatly appreciated.
> Thank you.
> Andrew
>
>
>