The utilization of high voltage electrodes in vacuum environments is common in a number of pulsed power applications. A limitation to voltage amplitude and/or pulse duration is flashover across the insulator separating the electrodes. Most often in cases where external effects are not involved, the cause of flashover is due to electron emission from the triple point, i.e., the junction of the cathode, insulator, and vacuum region. An approach being developed, in particular for application to compact electrostatic accelerators, is the elimination of the triple point through the use of bulk or film encapsulation techniques. Data from experiments will be presented showing that under both DC and repetitive pulse conditions (200 - 400 Hz), a simple bare-electrode accelerator structure that breaks down at 75 kV/cm in vacuum can be made to operate at fields exceeding 500 kV/cm by encapsulation. Candidate encapsulation compounds with reported dielectric strengths as high as 13,250 V/mil (thin film) will be discussed.