You will need
    • negalogenizirovanny fresh milk
    • separator
    • sourdough
If you want to make homemade sour cream, do not be lazy to look for milk, not subjected to factory processing. Dairies milk homogeniser, breaking the capsules of milk fat into tiny droplets, causing the milk remains uniform, not separated into cream and skim milk. That is, for your purposes it is absolutely not suitable.
Very well, if in your household there is a special device for separating cream separator. In this case, just skip the milk through it.
But if separator is not, then put a jar of milk in the fridge for 12-20 hours, then you will see how the cream rose up, separated from the more transparent skim milk. Carefully remove the cream with a spoon in a separate bowl.
Your further actions depend on what kind of sour cream you want to. You can just leave the cream in the fridge, they freeze in a thick sweet mass.
And can add a little yeast, and then your cream will become more soft texture and slight acidity.