Not that you read the post but the shit you put into powdered coke doesnt really make it into the crack. the cocaine and sodium bicarbonate are very soluble in water. When you heat it up the water and the crack crystalizes as it falls out of solution and cools. Sure some of the junk ends up mechanically in the crystal structure or coating it from the spoon. but if done properly and the rocks are picked out from the water and junk left in the spoon. crack cocaine is "free base" cocaine, essentially purified.
I cant go into too much more detail, but its basic chemistry 101. Cutting powder is easy as any white powder will do. But its a lot harder to cut rocks. Most cocaine dilutants (sugar, baby powder) are easily discarded from the crack making process. Adulterants are slightly more tricky but most you dont have to worry about as they arent any more harmful than the cocaine itself like lidocane which makes you think its more "pure" by numbing your gums/nose. Its not reactive enough to really become "crack". Levamisole is popular as it gives cocaine more of that "fish scale" look and has an amphetamine effect. But even though levamisole is as soluble in water as cocaine so it will dissolve during the crack making process, crack itself is insoluble and falls out of solution, leaving it behind in the water.
TLDR Saint Floyd watches over crackheads as the process of cooking crack protects them from impurities and adulterants.