I feel like it's as simple as slop is done without thought, but collage is planned. Once you just start to throw stuff at the wall just cause it looks vaguely correct but without thought or reason for why you're doing it it becomes slop.

I'm digging deep with my students on this in a few weeks; also why Burroughs cut-up is different; and why hip-hop sampling is different.

paLLMpsest

casserole vs. hot dish