Repulsion Gel is a light blue substance that repels objects. A player or an object that hits a surface coated with the Gel bounces off. Due to the effect, the height from which a player falls before landing on a Gel-covered surface affects the height of a jump. Players can also use the Gel to move back and forth between two parallel surface rather than merely be propelled up and down. Objects such as Storage Cubes and Turrets can be covered in Repulsion Gel which causes them to bounce around erratically.
Propulsion Gel is an orange substance that greatly increases object velocity and reduces the friction of objects moving on the surface(s) it is applied to. Objects covered in Propulsion Gel similarly have their friction reduced, causing them to slide around.
Conversion Gel is a portal-conducting white substance made from ground moon rocks. It enables the player to place portals on surfaces that are not normally portal-conductive.
Water
While not technically a gel, water washes off other gels from surfaces and objects. It has no special properties in regards to gameplay, and does not stick to surfaces.
Related achievements
Vertically Unchallenged Master the Repulsion Gel
White Out Complete the first Conversion Gel test
Stranger Than Friction Master the Propulsion Gel
Schrodinger's Catch Catch a blue-painted box before it touches the ground
Gallery
Gels
Repulsion Gel
Repulsion Gel
Propulsion Gel
Propulsion Gel
Conversion Gel
Conversion Gel
Water
Water
A Weighted Storage Cube covered in Repulsion Gel
A Weighted Storage Cube covered in Repulsion Gel
A Weighted Storage Cube covered in Propulsion Gel
A Weighted Storage Cube covered in Propulsion Gel
A turret covered in Propulsion Gel
A turret covered in Propulsion Gel
A turret covered in Repulsion Gel
A turret covered in Repulsion Gel
Trivia
The gel mechanic is a borrowed concept from TAG: The Power of Paint.
A fourth gel, "Sticky Gel", was also borrowed from TAG and was tested within Portal 2. It would have allowed players to "stick to a surface so you can walk up a wall like Fred Astaire in Royal Wedding"[1]; however, it was removed early on during development due to making play-testers motion-sick.[2]
Repulsion Gel was Aperture Science's first attempt at creating a dietetic pudding substitute.