It works fine at 40% lye concentration - I mix the soap till it is emulsified, divide into three parts. Divide fragrance into three too. Set aside to thicken slightly and make sure it's not going to separate. Then add the fragrance, mix it in thoroughly and quickly pour. It does accelerate, but slowly enough to allow for the swirls. I really like the fragrance, it smells really sophisticated. Like the jo malone candles of a similar name if you have ever smelled them.