After a discussion on a Facebook group page for OCA students to share their sketch work, I decided to look some more at drawing apps for the iPad. I have had Paper 53 for a while, which is good for watercolour effects. I invested a whole 69p in ArtSet, and have been pleasantly surprised with the results. There are a choice of colour and texture papers, and materials including oil pastel, oils, marker, and pencil. There are also various blending options. I hae a Wacom Bamboo stylus, but have had some good results using my finger alone. In the art world, the iPad has had exposure as a drawing and painting tool, particularly thanks to David Hockney.
Here are a couple of quick sketch studies I have made of my cats. As I hope is obvious, they have very different characters, and was pleased with the feeling of each sketch. The first cat is black, which based the decision to make most of the marks in the negative space.