I am looking for a process to etch Zerodur - glass ceramic. Until now I etched the Zerodur 'M' by Ammonium bi Fluoride and I got smooth surface and full transparency. Now I tried to etch the Zerodur by the Ammonium bi Fluoride but I lost the transparency and the smooth surface- actually the Zerodur 'M' block I etched is opaque. I tried to change the etching parameters – time, concentration an temperature but I did not succeed to get the transparency and the surface quality. Do you have any idea what to do ? Thank you