A number of possible routes can be used to prepare crystal violet. The original procedure developed by the German chemists Kern and Caro involved the reaction of dimethylaniline with phosgene to give 4,4′-bis(dimethylamino)benzophenone (Michler's ketone) as an intermediate. This was then reacted with additional dimethylaniline in the presence of phosphorus oxychloride and hydrochloric acid.
The dye can also be prepared by the condensation of formaldehyde and dimethylaniline to give a leuco dye:
:CHO + 3 CHN(CH) → CH(CHN(CH)) + HO
Second, this colourless compound is oxidized to the coloured cationic form (hereafter with oxygen, but a typical oxidizing agent is manganese dioxide, MnO):
:CH(CHN(CH)) + HCl +  O → [C(CHN(CH))]Cl + HO