@Lizzy1Fair there are many things can reduce a drugs quality & purity. If not cooked correctly, the quality will be affected in terms of purity and potency and byproducts from the cook may be left behind in the final product. Many dealers will cut the meth they get with MSM and N-ISO, an intermediate in the cook process, this will lessen purity
and therefore reduce the quality of the product.
Despite the types of chemicals that go into making methamphetamine, the end product won't contain those starting ingredients. They are used for chemical reactions that produce meth. None of the other ingredients are left in the final product. It's not as simple as saying "meth is made of Drain-O and the ends of matchsticks and other household cleaning chemicals", it is those chemicals that allow reactions to take place that ultimately form the drug that we all know and most love.