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In Elon Musk's recent Reddit AMA (ask me anything), he talked about
Initially, glass panes with carbon fiber frames
For colonization of Mars.
My question: Does a glass roof provide sufficient protection for plants/humans [against radiation] to create edible food on Mars?
Extra credit: Is ISRU glass production possible with minimal manufacturing capabilities? Or is spaceX forced to transport the glass? (Isn't glass heavy, and non-maleable making it difficult to transport?)
You don't want to filter out all radiation, of course - that's the point of using a transparent material. You want to filter out the high-energy part (UV) while leaving lower frequencies (visible light). Glass can do that, even better than air.
This doesn't filter out very high energy radiation which on earth are shielded by the magnetic field, but for crops that's probably not a major issue. They don't grow old anyway.
Glass is chiefly made from silicon and oxygen. As it happens, those are incredibly common on Mars, even more than iron. However, if we'd only use those, we'd get a problem with UV. With no additives, we'd make fused quartz, and that is very transparent to UV. Normal glass contains also a sizeable fraction of sodium oxide (soda) and calcium oxide (lime). Those two are fairly common on Mars.
Making glass is not too hard: melt the ingredients, mix, pour on a hot tin bath, let it cool.
