Optics with high resistance to laser damage are essential for operating high-power laser systems such as the Z-Backlighter lasers. However, the laser-induced damage threshold (LIDT) of an optical coating is generally lower than the LIDT of the optical substrate material. Laser damage can occur as a result of absorption of energy from the laser by defects in the optical coating or on the substrate. Producing an optical coating with a low number of defects and hence a high LIDT involves many variables, including the substrate preparation,8–10 coating material selections,5,6,11 deposition method,12 and the pressures maintained during deposition. Pressure is important because it must be low enough, with a vacuum pumping capability sufficiently high enough, to remove possible gas-phase contaminants from the coating chamber before they can attach to the coating and serve as defects that could increase laser damage. This study concerns pressure, specifically, the consequences of losing some vacuum pumping capability during a coating deposition. This is a concern because, on rare occasions, a vacuum pump requires maintenance and is taken out of service while a coating deposition is in progress. Until this study was conducted, we did not know how the loss of a vacuum pump would impact the LIDT of our coatings. This paper should, therefore, be of strong interest to those involved with the practical aspects of optical coating deposition for high-power laser systems.