in the repair of damaged shatterproof glass by the introduction of a polymerizable liquid into a conical crack a vacuum is intermittently released and reapplied to the damaged area by means of a vacuum chamber connected to a vacuum pump through a line having an opening to the atmosphere which opening is adapted to be rapidly opened and closed by an operator &# 39 ; s finger . the opening is threaded to receive a removable needle valve for accurate vacuum control . the vacuum chamber has a transparent end wall for viewing the work and a translucent cylindrical side wall allowing external light to illuminate the work without glare . a flexible seal in the end wall of the vacuum chamber allows a probe to be operated while the vacuum is applied . a plunger - sleeve combination , extending through the end wall is used to apply pressure to the liquid without releasing the vacuum .