|The eighth process of Sublimation consists of the purging of the original filth (produced by Putrefaction).|
During Sublimation, the alchemist heats the Stone in order for it to vaporize, then the vapour is quickly cooled and thereby condenses back into solid form.
This process is repeated a number of times. The purpose of doing so is to purify the matter.
The Stone needs to be so purified because it may have acquired contamination through the process of Putrefaction and later during the process of Cibation.
To the alchemist, this contamination is 'outward sulphur', which translates as the superficial soul which stands between ignorance (i.e. vain desires and motives) and enlightenment.
By way of repeated vaporization and condensation, the Sulphur can transcend from outward to inward spirituality.