This is oil on clear-primed linen (linen primed with a clear acrylic gesso instead of white gesso, it allows you to make use of the natural middle tone value of the linen). It is a fantastic surface to paint on. I did this small still life as a demo for my advanced oil students today. The top image is of the underpainting which I did in oil. The linen surface absorbs the oil quickly, enabling you to work directly on top of your underpainting with color with no problem of layers mixing and muddying colors. The brand I used here is Senso clear-primed linen, I would highly recommend it as an alternative to canvas, particularly if you enjoy working alla prima.
Oil on Linen