 Castle's artworks were created almost exclusively with found materials such as papers salvaged from common packaging and mail, in addition to food containers of all types.Castle mixed ink using soot from the woodstove and saliva and applied it with tools of his own making, including sharpened sticks, and other found objects.His drawings sensitively depict interiors, buildings, animals, landscapes and people based on his family's rural Garden Valley homestead as well as the architecture and landscapes of the places he lived and visited.