And wood glue! Looks like that method proved unreliable, so they expanded it:
"To create the mold, the mask is then used to expose the fingerprint structure on photo-senistive PCB material. The PCB material is then developed, etched and cleaned. After this process, the mold is ready. A thin coat of graphite spray is applied to ensure an improved capacitive response. This also makes it easier to remove the fake fingerprint. Finally a thin film of white wood glue is smeared into the mold. After the glue cures the new fake fingerprint is ready for use."