Form without content was one of the trends emphasised in the art of the 1960s. Coburn's art has never been without content but a lot of painting at that time was. American painting that was generally referred to as colourfield painting or hard-edged painting and artists like Kenneth Noland or Helen Frankenthaler very much influenced Coburn. While he claims a certain influence in this direction for some of his works, such as the painting Rainforest, there is conspicuous organic power and a homage to Nature.
"I suppose some of my paintings of this period roughly correspond to the hard-edged paintings of the sixties, but mine generally have very much more emotional content. I don't think I was ever terribly successful in eliminating emotional content, or ever really wanted to, although I was, at that time, striving for a colourfield, hard-edged effect. Rainforest, painted in 1968, had only two colours and very simple forms and it could quite well be described as a colourfield painting, but at the same time it has a fairly emotional content."