Sculptors across the United States are facing a material crisis. USG Corporation, the maker of Hydrocal, the specialty gypsum plaster that has long been a studio staple, announced in July that it will close its Oklahoma mine and processing plant and lay off its 250-person workforce, ending production of the product by the end of November.

Hydrocal occupies a rare middle ground in the materials world. It is durable enough to be used in metal casting and architectural restoration, yet soft enough for artists to carve and sculpt directly. That versatility has made it a quiet backbone of sculpture departments, casting studios, and restoration workshops. Beyond art, the plaster is used for dental molds, orthopedic molds, and the customization of prosthetic limbs.

The announcement has triggered alarm in the art world. Heather Rowe, the head of the sculpture department at the Rhode Island School of Design, told The New York Times that artists were "freaking out" over the news, and studios are now rushing to buy up remaining supplies while they hunt for substitutes. The problem is that no equivalent has yet emerged, and every alternative behaves differently in the mold and under the chisel.

Nate Bozeman, a ceramics technician at the Pratt Institute in Brooklyn, explained to the Times that artists and small studios depend on materials that are shared with much larger industries, so supply decisions made at industrial scale can ripple through the art world with little warning. Different plasters, he noted, require testing before artists can trust them with their work.

USG cited the "escalating complexity and cost to mine and manufacture the specialized products in the portfolio" as the reason for the closure. For sculptors, the coming months will be a race against the calendar: secure a stockpile, or find a new plaster before the kilns go cold.