Narrator: Cy Twombly created The Four Seasons from many different layers of paint, added over two or three years. Like most modern paintings they're unvarnished: so conservators can see and study the paint exactly as it was put on. But it also means that these works have to be very specially looked after. Tate conservator Patricia Smithen on the white and yellow canvas, 'Summer':
PT: "Twombly began painting these works by taking huge pieces of canvas. He cuts them off a large roll that's already primed. He marks a rough rectangle and cuts roughly around that and then tacks the canvases directly to the wall before he starts painting. And you can actually still see the tack marks - if you look along the top edge of the painting you can see these holes along the top. And that provides a really nice solid surface so he can actually be very physical with the canvases, he can really whack the paint on the surface if it's got a nice hard support behind it.
The paintings are made with a number of different materials: there's some acrylic paint, there's some house-paint, there's artist oil paints, graphite or pencil is on the surface. And he also uses an oil paint stick - which is a solid form of oil paint with a bit of wax mixed in and you use it essentially like a pastel - so you get a very soft texture on the surface - and because they're quite stiff you can write with them. And you can see on the left side of the painting these bright cadmium red scrawls on the left side and that's done in the oil paint stick.
Twombly applied his paints in different ways as well. He had quite a wide brush, we think it's probably about a 3-inch wide brush, to cover large swaths of the canvas in these transparent veils of paint. And he drips the liquid paint down. And he gets right in there throwing the paint on the surface and getting his hands in - you can see in the centre of the painting where his finger-marks dragged through the paint creating these ridges of paint. So it's a very nice physical interaction with the painting.
In terms of conservation they're very interesting paintings because they're in very good condition because they're very recent paintings. However there were a few problems that you'd expect to find when you're mixing so many different materials. On some of the canvases where you have thicker oil paint the paint as it's dried the paint has contracted slightly as it dries and you get this alligator cracking, these wide cracks as it dries. And in some cases some of the paint has contracted and slightly lifted off the surface. For conservation purposes what we've done is stuck a bit of glue behind these lifting paints and essentially stuck it back down to the canvas to make sure that everything's nice and secure.
The largest problem that we're going to have with these works is probably trying to keep them clean. We get a lot of visitors through Tate Modern and every visitor generates dust and that dust settles on the surface of our paintings. And with a regular painting, say a varnished painting, it's quite easy in some cases just to brush the dust away. On these paintings however, because they've got this graphic media - the graphite and the oil paint stick - it's really difficult to remove dust from the surface without removing any of that material. When they arrived into the Tate collection we did have to clean them, they did have a layer of surface grime. And what we do is instead of wet-cleaning them - rolling swabs over the surface that are dampened with water - we dry-clean them. So we use a very soft sponge that's dry, we wipe it across the surface to lift off any dust. And in this case we'd have to very carefully go around the graphite and the paint stick so that we don't remove any of that material."