Cleaning glass

I work in photovoltaics where we regularly use low iron glass. Part of our process involves the use of a silicone encapsulant upon which we lay a piece of glass for protection of the solar cells. we are having trouble bonding the glass to the silicone and I feel it is because our glass cleaning process is not vigorous enough. I was wondering if anyone out there could let me know how glass is cleaned commercially before the application of things like thin films.

Thanks in advance.

James