

Several areas in the Condemned Testing Facility seem to indicate that the Conversion Gel was used to paint all further testing facilities, explaining how only white-painted walls were affected by the Portal Gun.Īccording to a pre-recorded message from Cave Johnson, the Conversion Gel is made up of ground-up Moon rocks, as they are an excellent portal-conducting surface, although contributing to Cave's death due to being poisonous. Conversion Gel is a white fluid that allows the Portal gun to place portals on surfaces that would normally be unfit for placing portals.
