I've had a lot of requests for our juice kefir recipe so I'm posting a photo and instructions on how to make juice grains from your dairy grains. Juice kefir is extremely easy to make once you have the grains, and it's delicious. We've had success with using the same strain of grains for the past few years; we've even shipped them to a friend who started her batch and a year later she shipped grains from her batch to replenish ours when lack of feeding it "killed it."
Unfortunately, I don't remember the exact process but I believe we used Dom's instructions outlined below to take dairy kefir grains and transform them to juice kefir. Here are his instructions, with a link to the rest of the post:
Conditioning Milk-Kefir Grains to Sugary Water
✴ Transfer a portion of your milk-grains to a sugar solution (sugar-water, or diluted
raw white grape juice); see Kefir d’Acqua recipe below, for proportions. Ferment
as usual at room temperature, then strain and repeat.
✴ Note that the first few batches take longer to ferment, up to 4 - 5 days, while the
grains become accustomed to the new media (source of sugar). After 3 batches
or so, the grains should complete fermentation within 24 - 48 hours.
✴ Do not use all your milk kefir-grains, but only spare grains. Thereafter, always
use the water-grains for water media, and milk grains for milk. Don’t try to transfer
back and forth.
THE EASY PART: Once your kefir grains are usable for juice, add grains to a gallon (or less) of apple juice, leave out at room temperature for 12-48 hours (or less in hot weather) and taste a couple times a day. When it starts to develop bubbles, tastes pineapply, and looks a beautiful shade of pineapple yellow, it's time to refrigerate and enjoy. DISCLAIMER: there's an element of danger with it - if kept in a glass container tightly closed at room temperature for too long, it can explode (that's another story for another day!). I now use a gallon sized glass jar with a plastic lid not-so-tightly closed.
To revive juice grains that have been dormant: Feed it with sugar and/or apple juice every day until it starts to bubble again. Kept at room temperature. About a tbs of sugar every day in a quart size jar of apple juice/kefir grains should do it. It took us a good week or so until it bubbled. Then go back to "the easy part" and you'll have kefir for life :)