Measuring the volume of complex, organic, or irregular master models (such as pinecones, hand-carved clay structures, 3D printed figurines, or natural crystal formations) using standard geometric formulas is practically impossible. In craft workshops, this leads to the 'guesswork tax' where creators either mix too little material and ruin the mold box, or mix too much and waste expensive silicone, resin, or plaster. The water displacement method, based on Archimedes' Principle, solves this by measuring the physical volume of water an irregular object displaces when fully submerged.

to perform water displacement calculation, place a container filled to the absolute brim with water inside a larger tray. Fully submerge your master model. The volume of the model forces an equal volume of water to overflow into the outer tray. Since the density of pure water is precisely 1.0 gram per cubic centimeter (g/cm³), the weight of this overflow water in grams is exactly equal to the volume of the model in milliliters (ml). Once this volume is known, you can convert it to the required weight of any craft material—such as epoxy resin, silicone rubber, concrete, or Jesmonite—by multiplying the volume by the material's specific gravity.