I think I should clean the colloid mill well before use. I read on forums that these machines from China are rather dirty and greasy when dispatched for sale. Precision machining is their forte but not cleaning. Anyway, all the materials in contacts with food are made of high grade stainless steel. It is sure good to go after a decent wash.
I screwed out the hopper. Peeked on the stator and noticed traces of metal trimmings. I must clean it thoroughly. I carefully separated all the parts and also noticed the non-food grade grease on threads and seals. It is going to mix with oily cacao during grinding process. There were two things for removal, the metal dust and the dirty grease. What was said on forums was indeed true.
I washed the parts with soap and water. Rinsed dry. The grease that should be used in equipment like this should be food grade, the silicone grease. I don’t own that kind at the moment so I used petroleum jelly for the time being. I’m going to re-apply once a good silicone grease is in hand.
The colloid mill is now ready for the first production trial.