

This happy accident turns out to be a result of superheating, which is usually a reaction during saponification caused by the fragrance oil. The temperature gets shot way up and then the stress has to come out somewhere, so the soap bursts and cracks. In this case, they used a downspout and the high temps caused the soap to come out the top. Soap Queen did a great blog post on a coconut milk batch that superheated.
I've been around Anne-Marie when something unexpected happens and instead of being bummed out by it, she grabs her camera and gets really excited. It's great! Takes the stress right out of being attached to something you put so much work into, because after all, you might end up with a wonderful surprise in the end.