Would it be possible to use Kefir whey? I grow my own Kefir grains and have lots of whey from the process.
My first reaction to this is no. I am not very familiar with the moving the milk into kefir, but I think there is a fermentation process involved for 24 hours? (Tell me if I'm wrong and I will dive into this more.) The whey I am using in both skin creme and shampoo is fresh and free from anything being allowed to grow. Yeast + Skin creme in a big no. Preservative is added immediately and there should be no fermentation what so ever. I am in the process of documenting the shelf life of this recipe for longer than 4 months and I will post my results for the fresh recipe above for a 0 - 12 month time frame.
With that said, I'm thinking when you say -grow Kefir grain- you mean ferment the curd from the dairy. That is how I read it. However, please correct me if I didn't quite answer your question, because I am not very experienced with yogurt making.
@thermalmermaid So sorry this took so long, my son suffered a bad injury and I'm playing catch up (he is ok now). Yes, it is brewed/fermented dairy kefir that forms grains that you strain out to harvest, but I do it for longer than 24 hours, and strain it thoroughly, so it's very thick and yummy. Anyhoo, I didn't think of the preservative side of this and yes, this is an active ferment. I have used it in soap, but the lye monster takes care of the kefir critters.