In a letter (dated 14 July 1986), the artist wrote: "In the summer of 1967 I broke my right leg very badly in an accident in the sea at Lamorna Cove involving a canoe. My entire leg was encased in plaster for nine months - for four of which I afterwards discovered the surgeon had contemplated amputation at the knee. As a result I was unable to paint a single canvas for nearly a year - as distinct from works on paper, which could be done in a sitting position. When I finally started painting canvases again I for some reason decided very greatly to enlarge their scale, setting to work on a series of paintings measuring nine, eleven, thirteen and even fifteen feet in length. This painting was one of that series, all of which were exhibited in January 1970 at Waddington's original gallery at number 2, Cork Street, where they were slightly cramped for space, of course.

Unlike Rothko, who, in 1960, showed me the flat in Manhattan where he'd been living and painting until well after he'd enlarged the scale of his canvases to the familiar size of his mature style, with the result that his paintings were touching each other all around the walls of his living-room-cum-studio, as he explained to me - I, myself, have always needed very considerable space for showing my paintings. I've always felt that my canvases simply cannot be seen if they are not more or less isolated by expanses of white wall all around them. Rothko, in total contrast, actually prescribed very close hanging - about 18 ins. between each work. I therefore most enjoyed seeing this painting of mine at the Royal Academy's 1977 exhibition British Painting 1952–1977, where it was isolated on a specially built screen in the centre of one of the galleries, from where it was visible from down a vista of several rooms. The result was that it floated.

About the painting itself, it so happens that I mentioned it in the Power Lecture, entitled ‘The Shape of Colour’, which I gave in Australia in 1973. The following is part of what I said there: "For instance, in 1969, I arrived at a series of very large paintings ... ‘Cadmium with Violet, Scarlet, Emerald, Lemon and Venetian: 1969’ is an example. Looking back, the object here seems to have been to see how far a few of the familiar elements could be stretched out sideways, with this long horizontal composition (and there's a word, ‘composition’, we needn't run away from), without that largest area of cadmium-red disintegrating back into that vacuous background of neutral nothingness I so much despise! I used to say, as far back as 1959, that what one was looking for, in stretching out a single colour-plane across four-fifths of a canvas, was a full emptiness or an empty fullness. In these very long, very large paintings of 1969 and after, I think one has added to that earlier requirement of ‘full emptiness’ this new one: to see how big a colour-area can become physically while still retaining a visible compactness in its image, a tightness in its design and organisation that remains totally readable, despite the expanded scale of that design, of those images. How far could one expand one's colour-areas without appearing to be distending any or all of them? I have painted a version of this ‘Cadmium with Violet’, with the same colours but on a format only nine inches long. One of the mysteries of scale which seeing the two versions together would demonstrate is to do with what I call the physicality of mere size: the plain physical impact of a large painting, the sheerly quantitative bombardment by the vibrations of really big areas of colour - these constitute a totally new factor. It was simply a fact that, in painting large, one was entering a field of physical sensation which just was not given off by smaller paintings.

It used to be felt that two adjacent areas of flat but differing colours - say a red or a blue - would always take up a fixed spatial position in relation to one another along the line dividing them. It used to be said that the red would always appear to come in front of the blue. My own experience suggests that this is quite untrue. When your eye alights on the sharp linear frontier separating two colour-areas, your sensation that one of those colours is ‘nearer’ to you than the other - this sensation, this conviction that space-in-depth separates the two colour-areas, is overwhelmingly definite as a sensation. Its cause, however, is enormously difficult to pinpoint. In these large recent paintings such as ‘Cadmium with Violet’ one is extremely conscious, as one's eye moves along the frontiers of the various areas, that these areas actually alternate with one another (as one's eye moves) in seeming to be behind or in front of one another - according to whatever loop or angle in the frontier one happens to be focusing upon. For instance, the cadmium-red ground (if you'll excuse the term) does not appear to be uniformly either behind or in front of the more orange ‘harbour-shape’ which extends downwards from the top right-hand corner of the painting. On the contrary, as your eye slides round those outlines the cadmium and the orange [scarlet] appear to keep exchanging their spatial positions. In ‘Colour in My Painting: 1969’ I said ‘Complexity of the spatial illusion generated along the frontier where the two colours meet is ... enormously increased if the linear character of those frontiers is irregular, freely drawn, intuitively arrived at.’ It is the totally regular, the perfectly geometric lines between colours in the movement known as Op Art which distinguishes it entirely from my own-despite our shared interest in optical after-images, and so on. The after-image is for me merely a welcome by-product, not a calculated end-product."

The period of my work to which this painting belongs came to an end with the paintings I made for my retrospective at the University of Texas at Austin Art Museum during 1977, the year before that exhibition was held (1978). I called them ‘wobbly hard-edge’ when I showed in Australia. Since 1980 the interests pursued in my painting have moved away from the rather exclusive preoccupations described in the long passage from ‘The Shape of Colour’ which I've quoted above."