Art and/or design?

I have been working this past week at The Print Studio Cambridge on a series of new mono prints. These have given me an opportunity to explore screen printing and this in turn has provided a new experience of using the potential of transparency in my paintings. I will post some images and a further blog in due course. One offshoot of the work though was -perhaps - a more general  thought about the link or absence of a link between Art and Design, also their inherent characteristics. I began to wonder when does Art stop being Art and become Design? Can it change in this way or are the two discrete at all times? Also what is pictoriality? When do you know you are looking at a work of art? More to follow..