This cleaning procedure is applicable to optics that have residue that can only be removed by water based cleaning. This procedure depends heavily on the quality of DI water used, which is why it was abandoned as the aLIGO cleaning procedure for ground glass, in favor of a Freon wipe (see procedure E1200266).
V4 includes the following important safety note:
Chemical splash goggles shall be worn when using the ion gun to dry off methanol.
The ion gun should be de-energized by disconnecting from the power source for at least 5 minutes prior to the use of the gun to ensure that the gun in de-energized. The ion gun should be kept unplugged at all times when using around any flammable solvents such as methanol, isopropyl alcohol or acetone.