"The portals can be placed on almost any surface which is flat, white colored and large enough to accommodate them. Moving objects, or certain types of surfaces, will usually prevent the formation of a portal. Material Emancipation Grills will block any attempt to shoot portals through them, as well as reset any active portals should the ASHPD pass through it. "
"According 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."
"According 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."
My Work here is done.
via:
http://half-life.wikia.com/wiki/Aperture_Science_Handheld_Portal_Device
http://half-life.wikia.com/wiki/Conversion_Gel