Solid ink is a 3D material used in a single nozzle(Howtek squeeze style acoustical fluid chamber with sliced orifice) and also used in Multi-nozzle (bender or piston style fluid chambers with electro-formed orifice plates) inkjets. The Printheads must be heated. Wax based Solid ink will flow below 100C but Thermoplastic Solid ink prefers 125C (close to the piezo Curie, piezo poling temperature). Piezo manufactures still insist the operating temperatures are dangerously high but the Howtek printheads work fine. Howtek style inkjets were designed to use Solid ink in 4 minutes print cycles but are now printing full 3D models that may print for 1 or 5 days at drop frequencies near 16,000 dpi at times. The Solid-ink is liquid at operating temperature and acts like water with sound waves (slower than water) forcing drops out of the orifice in the Howtek style inkjet.