So this is what it looked like after 8 hours...
Place your rhubarb and raisins in the bottom of your sterilized jar. Add in a strip of lemon zest and one mint leaf.
Strain the mint leaves out of the brew.
Pour the strained brew into the jar with the rhubarb, mint, and lemon.
Close the lid...
The instructions read: "when the raisins float to the top, the kvass is ready." Okay. First I wasn't sure we could actually see the raisin. But he spied them on the bottom. "There they are, Mommy!!"
Into the fridge it went. I'm sure he'll be checking for those floating raisins everyday. Stay tuned for the next steps. I'd get in about 3-4 days.