Purity: Ruling on Doubt About Bubbling of Grape Juice

Practical Laws of Islam as per the teachings of Ayatullah Sistani

Ruling 198

Grape juice about which it is not known whether it has bubbled is lawful to drink. However, if it bubbles, it does not become lawful to drink until one is certain that two-thirds of it has been reduced.

-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)