You can get stone and plaster in the student lab on the first floor. To the right of the cashier is a narrow hallway. Walk 45 feet, the lab is on the right.
Always try to use a thicker (more powder) mix of stone or plaster. It makes for a stronger model with less bubbles. Use a vibrator and add plaster or stone to only one part of the impression. Watch it flow over the remaining denture area. I sometimes add stone (plaster) covering the tissue surface and then vibrate out (back into the bowl) some of the stone (plaster) just leaving a thin layer on the impression. This tends to remove bubbles. I then fill the impression again.
You can invert the primary poured impression on to a base of stone. You will not do this for the secondary impression. Inverting can cause the stone to pull away from the impression.
When pouring the mandibular model always pour a base which includes the tongue space. There is a possibility of breakage in the midline without the additional strength of the base.
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