Plastium

Plastium is an advanced plastic-like element used as a building material in Oxygen Not Included. It functions as a high-temperature variant of Plastic: structures that use Plastium as their primary construction material receive a +900 °C increase to their overheat temperature, the largest overheat bonus in the game (shared with Thermium). Plastium also has a phase-change (sublimation/melting) temperature far higher than Plastic (Plastic’s phase change is 159.85 °C), making Plastium suitable for construction in extremely hot environments such as those near the Asteroid core or volcanic zones. Despite these high-temperature advantages, Plastium is a poor thermal conductor and is not intended for active heat exchange; it is best used where thermal insulation or overheat resistance is required rather than for moving heat.

Plastium is produced only in the Molecular Forge. The Molecular Forge recipe is:

• 15 kg Thermium + 70 kg Plastic + 15 kg Brackwax → 100 kg Plastium

Because Plastium is classified as a Generic Buildable material for plastic-based constructions, it can substitute for Plastic in any building that lists Plastic as a permitted material. This substitution allows certain heat-sensitive Plastic-built devices to be constructed directly in hot areas where standard Plastic would fail; typical examples include the Mini Liquid Pump, Mini Gas Pump, Plastic Tile, and Steam Turbine (i.e., any building that would otherwise require heat-sensitive Plastic). However, Plastium will not change a building’s overheat or phase behavior if Plastic is not the primary material controlling those properties—some multi-material constructions determine overheat and phase targets from their most significant component (often a refined metal), so replacing incidental Plastic with Plastium may have no effect.

Plastium’s low thermal conductivity and very high phase-change temperature make it particularly useful for high-temperature insulation and for constructing components of nuclear power modules and other high-radiation, high-heat systems. It shares the game’s highest radiation resistance rating for Tiles along with Plastic, Lead, and Depleted Uranium, but Plastium’s much higher phase-change temperature and better insulating properties make it preferable for critical high-temperature nuclear builds. Mineral-based tiles can provide better raw insulation in some cases, but Plastium Tile consumes less mass for construction while maintaining greater thermal tolerance.

Practical notes and strategies:

• Use Plastium to build or tile around heat-producing installations where Plastic would melt or buildings would overheat; Plastium allows direct construction in environments that approach the high end of the temperature scale.
• Do not expect Plastium to perform like Thermium for heat transfer. Thermium is intended for efficient heat exchange; Plastium is an insulator and will hinder heat flow.
• Replacing Plastic with Plastium everywhere is mass- and resource-expensive; reserve Plastium for parts that must survive extreme temperatures or require high radiation resistance.
• Be cautious near the Magma Biome: Plastium’s sublimation/melt point is around the same temperature as the Asteroid core’s Magma Biome, so structures can still degrade if exposed directly to Magma temperatures.