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This article is about the gels. For the Portal 2 co-op chapter, see Portal 2 storyline#Mobility Gels.
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The Mobility Gels are special gels used by Aperture Science for testing. Appearing in both single-player and co-op modes of Portal 2, they come in three types: the Repulsion Gel, the Propulsion Gel, and the Conversion Gel.


Propulsion and Repulsion Gels are a derivative of fiberglass insulation designed to be sweeter and slightly less non-toxic. Cave Johnson makes mention of an additional, unknown element in Repulsion Gel which imparts its special abilities, however, Cave warns test subjects that this element "does not like the human skeleton." The gels were originally marketed as a dietary aid, but were quickly pulled from shelves following the disastrous results of their use on humans. The gels were then repurposed as a testing element in Aperture's Test Spheres. Each one has a different effect.

Repulsion Gel

The first kind of gel encountered is the Repulsion Gel. It is first found when Chell is making her way through Aperture's first Test Sphere, where (apparently) war heroes, astronauts, and Olympians were hired to participate in various experiments; one of which was the Repulsion Gel. As the name implies, it causes people and objects to bounce off of it.

Propulsion Gel

The second kind of gel encountered is the Propulsion Gel. It is first found when Chell and GLaDOS (still inside a potato after Wheatley's betrayal) make their way through Aperture's second Test Sphere, where (presumably) homeless people were offered $60 to for participation in various tests; one of which was the Propulsion Gel. As the name implies, it causes people and objects to move at high speeds while walking/running on it.

Conversion Gel

The third and final kind of gel encountered is the Conversion Gel. It was developed on impulse by Johnson; he purchased $70 million worth of Moon rocks and turned them into a gel with similar properties to the company's previous two gels. In doing so, he was fatally poisoned by moon dust. The gel, however, proved to be an excellent portal conductor. Cave decided that testing with this gel will somehow give the scientists a cure for Cave's illness. It is first found when Chell and GLaDOS are making their way through Aperture's third Test Sphere, where Aperture scientists were testing the gel. Being a "good portal conductor" as Johnson put it, it converts any surface into a portal surface.


All three gels share similar properties. They will stick to any solid surface, imparting their properties to that surface. If one type of gel is poured on top of another, it coats the earlier one, negating the properties of the first in favor of its own. The gels immediately wash off in water.

Each gel (apparently) has a harmful effect to it. Cave Johnson warns that the unknown element in the Repulsion Gel "does not like the human skeleton," and the Conversion Gel fatally poisons Johnson, as he said that "ground-up moon rocks are pure poison." However, the harmful poisons in the gels seem to have lost all potency over the course of several decades, as Chell can get splattered with the gels with no effect on her system.

All three gels were left in storage when the old Aperture Laboratories was sealed off. However, the new facility was equipped with pipes to connect to the gel supplies if the old labs were unsealed. This occurs when Chell makes her way out of the facility following Wheatley's betrayal.

Behind the scenes

  • The Repulsion Gel and Propulsion Gel are based on the paint featured in Tag: The Power of Paint. The third paint, allowing its user to walk on walls and ceilings, was playtested but ultimately scrapped, although its coding is still present within the game and can be enabled with the correct mods.
  • There were unused gels called Adheison Gel and Reflection Gel, Adheison Gel was supposed to let the player walk on walls and ceilings and Reflection Gel was supposed to act like a Laser Mirror.

List of appearances


  1. Tag: The Power of Paint official project page
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