The lost-wax path to pressable ceramic is 40 years proven — and a wax disc is the most controllable starting point.
Why pressable, why wax
Pressable leucite/ lithium-disilicate gives a monolithic, crack-resistant restoration with a fit that printed patterns still chase. A milled wax pattern gives you a predictable 0.1–0.2% burnout shrinkage.
Critical steps
- Sprue at the thickest point; a thin sprue chills and voids the coping.
- Use a phosphate investment matched to the wax's expansion.
- Burnout: 2 °C/min to 730 °C, 1 h hold — faster leaves ash.
Ash residue from a poor wax is the #1 cause of cloudy pressings.
Start with a low-ash wax disc graded for pressables.
Sprue like you mean it
- Use a 3–4 mm sprue at the thickest part; thin sprues freeze before the ceramic fills.
- Angle the sprue 10–15° off the button to let air escape.
- Invest with a phosphate-bound mass; vibrate 2 min to kill bubbles.
Press and divest
Press at the ingot's temperature (usually 920–940 °C) with a 10 min hold; a fast press traps a void. After cool, divest in an alumina medium — never sandblast the ceramic, you frost the surface.