break the surface, immediately drop heat to the lowest setting ($85^\circ\text{C}–90^\circ\text{C}$ / $185^\circ\text{F}–195^\circ\text{F}$). Cover tightly and simmer for 24 to 36 hours. Check the pot every 8 to 10 hours and top off with boiling water only if bones become exposed to air. Do not boil rapidly; rapid boiling breaks delicate gelatin polymers into fragmented liquid peptides that won’t set into jelly.
Instant Pot Alternative: Lock the lid, seal the valve, and cook on High Pressure for
