Artist Peter Doig on how he paints

I was never a 'start-with-a-fresh-palette-in-the-morning' type of painter, says Peter Doig
Mal d'Estomac by Peter Doig
Mal d'Estomac by Peter Doig, 2008. Distemper on linen. Photograph: Peter Doig. Courtesy of the artist, Victoria Miro, London and Michael Werner, NY Peter Doig

My paintings either start as images I have seen in photographs or things that I have photographed. I then might make a drawing with oil paint from the photo. The photographic element is usually only a part of the composition - something that involves perspective or dimension for which I need a reference; something that is distorted maybe and would be unbelievable if drawn straight out of my head. Having said this, I have been trying to get away from the photograph and use drawings or memory as a start.

Painting for me is very much about the material. I say this because I rely on materials being around and being used and visible. Paint tubes in a shop are the least inspiring things, but paint when mixed and congealed and getting old in pots and jars for me suggest possibilities. Sometimes rotten paint is the best (and something I couldn't ever intentionally mix). I was never a "start-with-a-fresh-palette-in-the-morning" type of painter. I react to what happens during the making of a painting. This is what determines when a painting is finished for me. I have no ultimate plan, really. I want to be surprised. I would get very bored if I followed a procedure.

Generally, my paintings are made with thinned-out oil paint. Over time, different areas are built up and made more opaque. The sense of light, space and mood of a painting does not come naturally (or by a known skill) but through working, and often by chance. This can be frustrating. The hardest thing for me has always been what to paint and why - I spend more time thinking about this than painting.

Peter Doig was born in Edinburgh in 1959. He is represented by Victoria Miro, London, Gavin Brown's Enterprise, New York and Michael Werner, New York