Emily,
I wish I could answer that accurately, but since I don’t have a high efficiency washer, I can’t answer that firsthand. I do have a friend that uses it in hers, and hasn’t had a problem, but I’ll just say use it at your own risk! 🙂

I usually use the powdered detergent to make the liquid detergent. I sometimes just throw in a couple spoonfuls of the powder if I am out of the liquid. It works just the same – you just use less when you make the liquid. I’ve never tried it in the food processor. I know you could do it with the Fels Naptha soap because it’s pretty soft, but the castile soap is quite hard. I guess you’d just have to try it and be ready to turn it off right away if need be!

so do you use the powdered detergent? or do you just make the powder and then turn it in to liquid? Have you found that liquid or powder work better?

I have also read about grating the soap in the food processor – can I do that or will it destroy my food processor?

I usually just add in a couple bars of castile soap to my vitacost.com orders, but I know I’ve seen it at Walmart. I think it was with the regular soap in the personal care section.

I really should do this soon. 😉

Interesting. Great that you figured out how to make it work!