(I assume you are talking about thermoplastic materials ...)
You can't. There are many different types of plastic that all have a different chemical composition. The way the long molecules are ordered is responsible for the transparency of a certain kind of plastic. If the molecules are unordered (amorphous) the plastic is transparent. If there are regions where the molecules are aligned parallel (semicrystalline) the plastic is opaque. Of course I'm talking about the pure plastic. As soon as it is mixed or compounded with other materials (e.g. color pigments) also amorphous plastics can become opaque.
Most of the semicrystalline plastics are transparent if they are melted. But that's probably not what you were talking about ...
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Simple, Pepsi, Orange and Tomato Juice
Maybe we don't have to use gorilla glass after all.
Nice find, You must have family in Ubergizmo.
What kind of plastic? Some you can, some you can't.
You can't materials are transparent because of their atomic construction. you can't change it.
For bricks it is quite easy, someone invented transparent squares as well as hinged ones.Not 100% sure but I guess they are called doors and windows, maybe worth a try?
No problem, just bring your light source and receiver into the X-ray or gamma ray range. Plastic is transparent for those.
Or just tell us a bot more of what you want to do. Crystal balls don't work the weeks before Xmas...