Use 6 ounces/180 milliliters (6.1  fl oz) if you are certain of the freshness of the starter. When in doubt, use a full cup of buttermilk as starter.  Shake thoroughly to mix. Label the jar with the date. This should take about 24 hours. If you find it takes longer than 36 hours, the starter was no longer active (meaning that the bacteria has died). The buttermilk may or may not be tasty if it takes longer than 36 hours but it can still be used for baking. This happens because the bacteria have fermented the milk, and the lactic acid is causing the milk proteins to thicken. Refrigerate immediately.

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Write a summary of the previous text in Indonesian:
Masukkan ragi (starter) bakteri berupa 180-240 ml buttermilk kultur segar ke dalam botol kaca bersih. Penuhi botol dengan susu segar. Tutup botol dengan rapat. Letakkan botol di tempat hangat sampai mengental. Pastikan buttermilk kental melapisi botol kaca.