Likewise the distinction between light (low wax content) and heavy crudes are important for similar reasons, most refineries cannot process both equally well.

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Light crudes have low wax content, with lower density and API viscosity.

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In 1667, Paris became the first city in the world to light its streets, using wax candles in glass lamps.

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The student prize went to Swansea Metropolitan architectural glass MA student Rhian Haf of Gwythevin, Abergele, for her glass sculpture Glass, Light and Space - a group of glass houses cast using an ancient lost wax technique.

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Heavy crudes (high wax content, high API viscosity, high density) cannot be refined efficiently by refineries geared to refine light crudes and vice versa.

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