Detergent can rip off the oil, but the hot water and the tumbling actually change the structure over time. This will transform your wool into felt. Felt is made by applying pressure and hot water. When you make your own wool, you seperate two different length of fiber. The long one are spun and the short one are use to make felt.

I always heard it was the mechanical washing/drying motion causing the hairs to act like tiny zip ties.