I am contemplating building one of my kilns to handle the temperature/length of time situation. What would a reasonable price range for large lenses be? Could I use clear float glass (ie not green or blue colored) How thick a blank is required if I have slumped/bent/cast the glass close to the curvature you need? As a total newby to the idea of telescope making I need to know what the commonly requested specifications are for say 30 inch diameter lense/mirror blanks. If I know that I will probably be able to make it. Kevin