Jesmonite AC100 & AC730 Mix Ratio Reference Chart & Batch Math

Jesmonite AC100 is an acrylic-modified gypsum composite. The chemical hydration reaction requires 2.5 parts reactive powder base (hemihydrate gypsum with setting catalysts) to 1.0 part pure acrylic polymer emulsion by weight. For every 1,000g of total mixed wet slurry, you need exactly 714g of Base Powder and 286g of Liquid. With a wet specific gravity of 1.75 g/cm³, 1,000g of wet mix fills 571 mL of mold cavity (or 1.75g per 1 mL of volume).

Jesmonite aqueous pigments are highly concentrated organic dispersions. Adding too much pigment interferes with the crystalline cross-linking between gypsum micro-crystals and the acrylic polymer lattice. Maximum allowable pigment is 20 grams per 1,000 grams of total mix (2.0% by weight). Exceeding 2% causes severe surface chalking, unbonded pigment bleeding, delayed cure, and friable edges that chip under thumbnail pressure.

Jesmonite powder must be added progressively to the liquid under agitation using a high-shear blade attached to a workshop drill at 1,500–2,000 RPM. Hand stirring with a tongue depressor fails to wet out micro-agglomerates, resulting in dry white powder lumps inside the cured cast. After mixing for 60–90 seconds until silky smooth, tap the mold firmly or brush a thin coat of slurry into fine mold details with a stiff bristle brush to pop trapped surface air bubbles.