Hello. Some time I've been doing research with aluminum mirrors.
With the technique we developed, many mirrors have been made, all with accuracy better than 1 / 4 lambda, for use in the visual spectrum.
The technique developed by us, differs substantially from that used for the mirror glass. Last year some aluminum mirrors made by us, were presented at ENAST (Annual Meeting of astronomy in Brazil).
Due to the interest in these mirrors, we founded the group:
http://br.groups.yahoo.com/group/ATMmetalmirror/
for all who are interested, can learn the technique and participate in discussions. On my page you can see a Ronchi / Foucault one of the mirrors as well as other photos:
http://marcosbaun.multiply.com/photo...onchi_Foucault
JMBaungartner