gresstust

Gresstust is a term used in speculative fiction and worldbuilding to describe a deposit or crust that forms on surfaces exposed to a mixture of oil-based residues and fine particulate matter. The name combines grease and dust to evoke its sticky, powdery character.

In-fiction, gresstust appears as a multilayered material: a glossy, viscous layer that dries into a dull crust; embedded fibers and mineral grains; and occasional micro-crystal growth. It commonly originates from leakages in industrial installations and from atmospheric deposition in varied climates. Its rheology ranges from tacky to brittle, depending on temperature and age. Chemically it is modeled as a complex organic–inorganic composite that traps pollutants and can influence local corrosion processes.

In narrative and game design, gresstust is used to convey neglect, entropy, and the persistence of man-made systems. It can impede equipment by sticking moving parts, clogging filters, or altering heat transfer. Some settings depict organisms that have adapted to colonize gresstust as a niche habitat.

Etymology and usage: The term is a portmanteau of grease and dust; it first appears in science fiction and worldbuilding circles in the late 21st century and has since circulated in guidebooks and RPG sourcebooks as a fictional material.

Related terms include patina, crust, encrustation, and contamination layer.