1. Make a preliminary impression in a stock rim-lock tray using irreversible hydrocolloid, and pour in dental stone (Fig. 2). The tray is extended with plastic modeling compound and sprayed with an adhesive.t 2. Adapt one thickness of baseplate wax relief to the denture-bearing surfaces of the lubricated cast. 3. Construct a custom impression tray with autopolymerizing acrylic resin. 4. Remove the tray from the cast with the wax spacer inside, finish, polish, and perforate with a No. 8 round bur (Fig. 3). 5. Border mold the custom tray in the mouth with green stick modeling compound. 6. Remove the wax spacer from the tray. 7. Spray the tray with adhesive. 8. Make the final impression with vacuum-mixed irreversible hydrocolloid. A. low water-to-powder ratio (62 cc roorn-temperature distilled water to 28 gm powderx) is ideal for this impression. 9. Cleanse the impression, and immerse briefly in 2% potassium sulfate solution (Fig. 4). 10. Box the impression on a plaster patty with boxing wax, and pour with vacuum-mixed dental stone.