'The paintings have become more structured, very controlled, almost completely planned. In an exposed painting I know the proportion I want. Then I make a line. That's the instinctive part - knowing where to leave it. The line is always made from the bottom of the canvas to the top. That way I can control it.'
Although the results call to mind the 1950s hard-edge abstraction of Kelly, Smith and Noland, Innes is careful to avoid admitting direct influence. 'It's important when you work within a language and a territory that someone else has worked in that you develop that language yourself. But I do have artists that I look at - Fontana, Cezanne, Newman, Rothko.'
Like all of these painters, Innes's work derives from his figurative training. 'When I make a single line in a painting I see it as figurative. A line has the same kind of tangibility as a life drawing. People can look at my works as hard abstracts, but they're also incredibly physical, personal paintings. To me, exposing a canvas is like exposing a part of yourself.'
So is there a direct connection between Innes's new paintings and perceived reality?
'I don't deny a metaphor. And sizes are important. The largest canvas is 1.9 metres wide, which is my span. It's not deliberate, but I don't feel I should go any larger. Then the viewer comes in. A piece of work is only finished when a viewer has spent time with it. I think it's very important that a work has a spiritual quality. I take a lot of personal thought to my paintings. Each painting is only done when it feels right. That's why there are so many series. I don't do five exposed paintings at one time. I go from exposed paintings to 'quotation' paintings to 'repetition' paintings.'
Apart from the increase in size, the obvious change in his work is the limited introduction of colour. He does not see this as radical.
'There's always been colour in my work. When I was doing the white paintings, I always read them as colour-field paintings. White on a canvas ground has its own colour. The ground comes through the white and the way in which that reflects light involves colour. Last year, I did one yellow painting. Yellow is an extreme colour. I wanted to push my painting to another extremity - to go quite hard.'
Does colour imply a new decorative quality? 'I tread a thin line between the work being decorative or not. I'm always walking a tightrope. If it's just decorative, well, forget it. But if a work sustains a tension that comes from the structure and the line, it can be decorative-aesthetic - and also have a reasoning behind it. I don't know where this new work is taking me. But it's nice when you surprise yourself.'
Callum Innes. Born Edinburgh 1962. Grays School of Art, Aberdeen; Edinburgh College of Art. His work is included in 'Wonderful Life' at the Lisson Gallery, 52-54 Bell St, London NW1, to 16 Oct