This ashtray is made of prisms glued together, the form is achieved by milling into end grain. This ensures higher safety against ignition, but of course you still shouldn't leave the ashtray without supervision.
We deliver the ashtray without any surface treatment and also don't recommend any further treatment to ensure maximal resistance against ignition. The fire resistance has been tested in usual usage, including the burning out of a cigarette in the ashtray.