When a company determines what content to add to their clay, concrete or plastics this is like a restaurant's secret recipe. These recipes can sometimes be closely guarded secrets that only a few people are aloud to know.
A manufacturer often has a team of experts formulate these recipes. Each plasticizer to be measured to the smallest degree possible. This recipe to be tested again and again against other possible recipes.
Once the best recipe is created and you know the best mixture of plasticizers to make the best product, production can be ramped up.
The best part of this recipe is that if followed correctly you get consistency. Consistency means that all your pots, ashtrays or bowls come out the same as the prototype.