All Pictures
The demise of USG plasters!
If true, this is seismic for ceramics.
The ceramic industry depends on some surprisingly specialized materials made by very few companies. When one of those companies exits the market, we need to notice. Consider how much of ceramics depends on plaster: slip casting of pottery and sanitaryware, jiggering, RAM pressing, mold making and countless studio processes. Yet plaster is so inexpensive and familiar that we tend to forget how technologically specialized—and indispensable—it actually is. USG #1 Pottery Plaster has been an industry standard for generations.
The Bad News
USG is closing its historic Southard, Oklahoma gypsum operation, apparently ending production of a wide range or specialty plasters including #1 Pottery Plaster, Hydro-Stone, Ultracal, Hydrocal, Puritan. This is a potentially seismic event for ceramics.
There is Hope
The core mineral in wallboard and pottery plaster is calcium sulfate hemihydrate. Historically, some gypsum plants produced both wallboard stucco and pottery plaster from the same gypsum source, separating the streams after calcination and tailoring each to its intended application. So maybe USG could make No. 1 Pottery Plaster at one of its wallboard plants. Unless there is something unique about the Southard process or the raw gypsum or reports of them "ceasing all industrial plaster operations" are accurate.
There is an Alternative
Fortunately, there is another major North American producer: Georgia-Pacific. Its K-59 Pottery Plaster is a remarkably close counterpart to USG #1, having essentially the same normal water/plaster ratio and density, with similar strength and expansion. Without products like these from Georgia-Pacific, the USG withdrawal could have been a genuine supply-chain earthquake for ceramics. Instead, it should be a wake-up call.
Cautious Optimism
Georgia-Pacific has a long-established Industrial Plasters division with dedicated sales managers covering both the U.S. and Canada. GP already manufacture pottery and tooling plasters, ceramics is one of the industries they explicitly target. If they decide to embrace the opportunity, they would become the primary North American supplier of specialty ceramic plasters. The biggest uncertainty is whether they can produce enough to replace what USG has historically supplied. And whether ceramic suppliers will begin stocking much larger inventories.

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