[extempore]

The phrase “black art” in the paper refers to a technical challenge which only experts can tame, via methods which aren’t widely known. It has zero to do with ‘black arts” in the sense of witchcraft. The blog post drifts between these meanings, possibly with poetic intention.

[bsanr2]

Perhaps the use of "black art" rather than "technical challenge which only experts can tame" in the paper implies poetic intention on their own part?