I was reading an article Meet the Artist Who Blows Things Up for a Living
in 4th paragraph the author says
When I visit Cai (as everyone calls him, pronouncing it “Tsai”) in his spare East Village Manhattan studio with a big red door and a feng shui stone lion guarding the entrance within, we sit at a glass table flanked by wall-size wood screens: his gunpowder “drawings.”
I didn't understand why author puts drawings in double quotes. If you read the article, he has used it for many other words like “signs”, “crop circle”. My question is what the intends by putting the words in double quotes?