What makes surfaces portal-able?
In Portal and Portal 2, only some surfaces are portal-able (generally depicted as white). In addition,
moon rock/gel/dust
seems to conduct portals very well. But is that the only thing?
It seemed that they had portals before the above discovery, but I can't find any hard evidence.
What defines a portal-able surface?
(i.e. all portal-able surfaces are white, but I doubt painting something white is all that is necessary)
Best Answer
Throughout Portal 1 and 2, we have observed several surfaces to be capable of carrying portals. Besides the white test chamber panels which are obviously designed for the purpose, concrete has often been sufficient to carry a portal, and we're also informed that moon dust is an excellent portal conductor.
My hypothesis is that portals are best conducted by silicon oxide compounds (particularly aluminium-silicon-oxide, which is the primary form found on the moon's surface). Concrete certainly falls into this category, as it is essentially manufactured from terrestrial rock which, like most rock, is composed of silicon oxide compounds. Other materials such as wood and metal contain almost no silicon and cannot conduct portals. Metal seems to be often employed when a strictly non-portal surface is required, perhaps suggesting that electrically-conductive metal is able to earth / short out portal energy to ensure that a portal cannot form.
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