What causes this?

Over the years, I have seen this from time to time and suspected that the black marks on my vanes (which bore an amazing resemblance to barred feathers) was caused by fletching contact. However, 2 days ago, I had all 3 vanes get this look after just one shot. Even the top 2 vanes now appear to be "barred" and I shoot a dropaway! I had just spray painted some big black dots on a cardboard target face and it wasn't quite dry yet, but that seems unlikely too.

Any ideas?

VooDoo magic...

Happened on all 3 vanes... That's deja vu...doo. [8D]

Are you saying you buried the arrows in your target, past the vanes? That's an easy one to figure out. The target smashed the vanes down, wrinkled 'em up and heat from friction slightly melted the edges of the wrinkles. The black paint was just icing on the cake. You made tie-dyed vanes!

Groovy

I've shot vanes through the edge of a bag target and ended up with the same situation....barred looking, but easy to figure out it you're passing those vanes trough something.