Hmmm...I didn't know it was a dark art. If it is considered a dark art, it would only be for two reasons that I can think of.

Firstly, it is a method of influencing another person (which can obviously be abused, if the other person is a vibrational match to that kind of abuse) and, secondly, it has some associations with the seduction community, because that community is all about influencing others, but the process itself is an NLP (Neuro-Linguistic Programming) one.

But, in that case, conversation, buying gifts and taking people out to dinner should also be considered dark arts because they can also be used to influence people ...and let's not forget those mega-industries of overt/covert human influence...Advertising and Marketing :)

Fractionation is simply the process of taking someone else into and out of a mental state rapidly and thereby intensifying that mental state for them.

If you mentioned Fractionation then I assume you have some NLP knowledge so I'll talk in those terms...

Let's say I anchor someone to some good-feeling state. If I trigger the anchor, they will obviously move into that state to some extent. Now if that state only had a slight intensity when I set the anchor, the triggered state will probably also only have a slight intensity.

If I wanted to increase the intensity of that state, I could apply Fractionation.

This means triggering the anchor, allowing them to move into that slight state, then move them into another (probably neutral) state, then trigger the anchor again, then back into a neutral state, then trigger the anchor again...and so on.

Each time the state is retriggered, it becomes more intense.

Hope that helps.