A-1100 is an amino silane that has been formulated specifically for aiding certain epoxies in bonding to the silica inherent in glass.
The actual A-1100 amino silane is combined in a mixture of reagent grade Isopropyl Alcohol. When applied to your glass pieces, the Isopropyl Alcohol will evaporate leaving a thin film of the A-1100 on the surface of the glass. This will look somewhat like an oily residue, but will completely disappear once the piece is bonded.
We normally recommend the A-1100 if you are bonding any surface areas over 2 inches. Smaller surface areas and crack filling generally do not require the use of A-1100, but it is cheap insurance for your bond joints.