The pyrex pot, rolled up my sleeves
Turn one into two like a Siamese
Twin when it end

from Jay Z – Blue Magic Lyrics on Rap Genius

Meaning

Jay cuts his product (most likely with baking soda), though why somebody bragging about having fishscale in his veins would admit to this is beyond me

Using the pyrex pot, he can dilute some quantity of crack cocaine 1:2. This is apparently quite difficult to do, while maintaining the (purported) “quality” of the product (more likely preserves the false authenticity)

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