5yr kid loved this video making stove from scratch so we made similar one using 3d printer. Total volume was 0.819 litter and I used 1kg of heat resistant plaster with water ratio 46～50％=0.83〜0.87 litter.
Total volume of total mass (でき高) (L)＝ Volumen of calcined plaster (焼石膏) (kg)×(0.37＋water ratio (混水量)(%) / 100)
3d model is at Fusion360 gallery.
She also loved this and respected them.
https://twitter.com/kaiordiie/status/1541535444352937984