This is a hybrid sketch: The exhaust duct and its shadow were rendered in black with a fine-tipped ink pen. The background is colored with watercolor paint.

Please visit my Etsy shop for my artwork for sale inspired by my autistic brother Mike at: etsy.com/shop/AutismInspiredArt.

My other artwork for sale is at: Etsy.com/shop/OtherArtbyJack