I was under the impression from some of the quotes in Portal 2 that the portal gun only worked on surfaces painted with moon-dust paint, or other moon-related surfaces. However browsing through Portal 2 quotations, I'm not sure that moon-related surfaces are technically a requirement. I can't recall/find any in-game references to prove or strike down this point.

So: is lunar material a requirement for the surface when forming portals produced by the portal gun found in Portal/Portal 2?

  • Are you asking about gameplay, or game story? We handle the backstory for games, but Arqade handles gameplay mechanics.
    – phantom42
    Commented Aug 19, 2015 at 20:33
  • 2
    This is 100% a story question, not gameplay. I'm wondering this as an in-universe question, @phantom42.
    – Ranger
    Commented Aug 19, 2015 at 20:34
  • Cool. Your half-life tags threw me as I haven't played those games yet.
    – phantom42
    Commented Aug 19, 2015 at 20:38
  • The requirements were: 1 - solid surface, 2 - porous surface. So drywall and concrete were easy. Metal sheets were not. Moon dust gel was a great conductor, that's why it still worked after being a liquid sloshed all over. Unfortunately, I can't find reference for any of this.
    – Radhil
    Commented Aug 19, 2015 at 22:48

2 Answers 2


My impression is that other materials also worked. There's a brief extro in Portal 2 where Cave speaks about his experimentation with Moon Dust:

"The bean counters told me we literally could not afford to buy seven dollars worth of moon rocks, much less seventy million. Bought 'em anyway. Ground 'em up, mixed em into a gel."

"And guess what? Ground up moon rocks are pure poison. I am deathly ill."

"Still, it turns out they're a great portal conductor. So now we're gonna see if jumping in and out of these new portals can somehow leech the lunar poison out of a man's bloodstream. When life gives you lemons, make lemonade. [coughs] Let's all stay positive and do some science."

The implication is that if there are new portals (e.g. where moon dust is used as the conductor) there must have been old portals where it was not.

And to quote directly from the developer's website:

How do I let people place portals on concrete next to metal surfaces?

Any place where a concrete surface is flush with a metal surface, create a func_portal_bumper brush entity 32 units wide next to the concrete and over the metal.

Obviously this doesn't preclude the concrete being made from moon rocks, but it seems unlikely.

  • 5
    Poor Cave Johnson. His story always made me sad. Commented Aug 19, 2015 at 20:48
  • 3
    Speculation: Regolith (ok... Moon Dust) is primarily a fine silica powder with a bit of added iron. Breathing in respirable silica like this causes the fatal disease silicosis. One major outward symptom is coughing. There is no cure so I imagine he would look for a longshot one. SiO2 is also pretty much just crushed quartz, granite, or most anything else which is used as a filler for concrete (most I said).
    – kaine
    Commented Aug 24, 2015 at 19:49

Moon rock can't have been required, because Aperture built the first Aperture Science Portable Quantum Tunneling Devices in the 1950s, before moon rock was available.

I think this image is not canonical, but the small graphic in its lower right corner is based on ones that appear in the game (see 2nd picture).

enter image description here

This image appears in the 1950s area of the game.

enter image description here

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    For the record, it's possible to collect moon rock from places like Antarctica, ejected from the moon in impacts.
    – Valorum
    Commented Aug 20, 2015 at 7:14
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    Also, in the universe of Portal, people went to space at least a decade earlier than an our universe.
    – Rogue Jedi
    Commented Apr 18, 2016 at 20:13
  • @RogueJedi Interesting! I've only played the game, don't know any of the extra material. Where is this early lunar landing described? Commented Apr 18, 2016 at 20:45
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    @OrganicMarble It's in-game. In our world, man first went to space in 1961. However, in Portal 2, the 1950's area of Aperture mentions astronauts performing test.
    – Rogue Jedi
    Commented Apr 18, 2016 at 20:54
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    @OrganicMarble In Portal 2, astronauts are already famous. So if they had only been selected less than a year ago, and had yet to go to space, that wouldn't make sense.
    – Rogue Jedi
    Commented Apr 18, 2016 at 21:13

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