The temple incense is made of 11 different ingredients. As found in the book of Exodus 30:34, only four ingredients are mentioned such as balsam, onycha, galbanum, and frankincense. So far in the study, the seven unmentioned ingredients have been passed down in oral way. The reason behind that it was not written is because of the rare kind of ingredients that can be obtained only from far places.
The preparation of the recipes was closely guarded and only a certain exclusive family can do it and passed down from generation within the ranks of the family. The manner it was prepared and the amounts mix were also secret. During the ceremony, the smoke of the incense raised up to heaven in straight column. It is speculated by some researches that they were using a plant that probably contains nitric acid because smoke produce by nitric rise straight upward.
The Sanhedrin was the one appointing the family to prepare the incense and the family assigned to do was called Avtinas. The Avtinas prepare the incense in a hall called Chamber of Avtinas.
The experty of the Avtinas in preparing the temple incense could raise the smoke straight upward. According to some expert in Alexandria, the smoke of their incense diffused and scattered instead.
The temple incense during that time was considered as holy; thus, until now it remains secret and never copied.