“Surface Tension is directly concerned with the elements of film projection: the film frame, the screen, and the projector shutter. A camera filmed the frame of light case from a projector running without film. The camera zoomed-in and –out, towards and away from the centre of the frame, and the filming speed was varied: at high speed (producing ‘slow motion’) the film catches the opening and closing of the projector shutter, and this produces the intermittent flicker on the film. After printing the film many times to increase the image contrast to pure tones of black and white, a negative and identical positive print were produced, and these are projected one on top of the other in the film presentation. Theoretically, the negative image should cancel the positive to yield a clear screen, but in reality, the inevitable fluctuation in projector running speeds generates a tension between the paired rectangles of light which become superimposed as oscillating off-registered edges. There is a soundtrack on both the positive and negative film print, and these are played through separate speakers. The soundtrack is the picture, the picture is the sound. The centre of the picture area has been printed directly onto the optical soundtrack edge of the film” – William Raban