Hardness is measured on the . Lower numbers are softer and more flexible: Mold Making and Casting Products by Category - Smooth-On
Generally considered the "gold standard" for its extreme dimensional accuracy and longevity . It has virtually zero shrinkage (around 0.04%) and can last for decades. buy silicone for mold making
Watch out: It is susceptible to —if it touches sulfur (found in some clays), latex, or certain 3D prints, it may stay gooey and never harden. Hardness is measured on the