Just for the newbies or people who are thinking of replacing their exposure glass.
I read somewhere that iron free glass can cut exposure time in half.
So I bought a sheet and replaced my normal glass.
I cut my exposure time on my home-built Metal Halide (1kW) from 12 mins (very old lamp) down to 6 mins.
Not just that, there is no slime on the ink side of the screen anymore.
Hopefully I can shorten it down even further when I buy a new lamp.