Labels that describe which glass is contained within the Insulating Glass Unit should be able to be removed easily, however, if there is some residue we would recommend that the glass is cleaned with a clean cloth and a clear non-abrasive cleaner, such as clean soapy water or a proprietary window cleaner.  For glass with a patterned, etched or sandblasted surface, a stiff bristle or nylon brush can be used to remove dirt from the recesses in the surface.
 
If the glass does not become clean using the above methods the following can be tried:-
Use a mild acid (e.g. vinegar) or a mild solvent (e.g. methylated spirit), taking care not to spill any of these on other surfaces or materials.
 
If neither treatment works then please contact your installer as the glass may need to be abraded and re-polished.  The process may result in some optical distortion where the glass surface has been removed and is likely to be expensive so should be left to the experts.  Please consult your window installer in the first instance. 
 
Special Notes on Cleaning
 
We recommend avoiding organic solvent cleaners on mirrors since they may attack the backing paint.
 
For patterned glass, acid etched glass and sandblasted glass, this should only be cleaned with a clear non-abrasive cleaner.  Any insoluble material in the cleaner may deposit in the recesses of the etching or sandblasting and may be very difficult to remove.

We advise that leaded glass should only be cleaned with a clear non-abrasive cleaner and the cleaner should be of a type that does not remove the patina (aged surface finish) of the lead.