High fidelity replicas of most well-stabilized museum objects can be made safely using silicone molds. Silicone caulking compounds formulated without acetic acid are now readily available, inexpensive, and conveniently dispensed from standard 300 ml cartridges. A complete mold can be made in one to three days, depending on complexity. The mold is dimensionally stable, with no discernable shrinkage, and expected mold life is measured in decades. While less elastic than latex rubber, silicone is compatible with all casting resins.