Painted Knowledge: An exhibition of painted information

This exhibition proposes to examine various forms of printed/published material that utilises the painted image as way of illustrating various forms of knowledge and narratives. This includes scientific diagrams, educational charts, natural forms, imagined stories and scenarios.
I am particularly interested in the early to mid-20th century period when there was a push-pull between the use of photography and paintings/prints to illustrate an idea or story in a book or piece of ephemera. Due to the lack of technology that would allow the manipulation of the illustration before printing most illustrations were made as the ‘final thing’; basically what would be in the printed publication perhaps with the addition of some text. Because of this many of these illustrations are highly skilled works and the images themselves can be stunning. I would like to examine the distinction between the painted image and a photographic source and why the publishers might favour one over the other and the effect this would have on the final look of the publication and the effectiveness in ‘getting over’; the point that was trying to be made.
Books or ephemera in the exhibition would be primarily sourced from those in the Centre for Research Collections at Edinburgh University and this would be supplemented with some of my own collection including some specific publications including those by Collins including the Pageant of Knowledge series, the series of Encyclopaedias called Pictorial Knowledge, The Ladybird book series, Knowledge magazine and the How and Why Wonder Books.
I also hope to show various forms of educational charts, some of which would be made as a permanent fixture of a classroom and would show a particular piece of information and the more widely available Indian charts such as those printed by the Indian Book Depot. These educational charts cover a huge range of subjects and aim to get various narratives and information across by being both attractive and strikingly designed.
If possible I would like to include original artwork for some publications if it is available. This would involve a bit of investigation of various archives across the UK. There are 2 main points about that; how was the artwork technically made? And how does the look of the original painting correspond to the final printed/published version?