Raspberries are soft and fragile so don’t rinse them under running water. Spread them out on a tray and pick over the fruits with your fingers removing leaves or twigs, and then you can prepare the juice. Remember, fermentation removes pesticides and chemicals during the fermentation process.
Place all ingredients into a glass jar or ceramic pot that does not have lead-based paint and is food grade. It should hold at least a gallon with enough extra room for air circulation. Gently mix the ingredients well.
Cover the lid with a cloth or napkin and secure it with a rubber band. Leave it out at room temperature. Place in a warm spot (68 to 70°F) for 3-4 weeks. It will gradually take on a distinct vinegar smell and you will notice a slight film on the top. If you get a white foam or yeast on top (kahm yeast which is harmless) this means it's ready to remove the berries.
After 3-4 weeks, strain out the raspberry solids, then pour the mixture into a half-gallon mason jar.
Cover with a cloth and continue fermenting for another few weeks or longer until the vinegar is tasting tart. When it tastes sour like regular vinegar, screw a lid on the jar and store it in your cupboard or pantry, or bottle it in smaller jars.
Once it’s bottled, you can store your vinegar wherever you like. It is shelf-stable and will last for 1-2 years. Over time, the flavor and acidity will mellow out. But it’s so good, you probably won’t be able to keep it around for long!