How do you mend a torn Picasso?

An art student fell into Picasso's The Actor at the Metropolitan Museum of Art in New York this week, creating a 6in tear. How can it be fixed? Modern-paintings specialist Michael Robinson, from conservators JH Cooke and Sons, explains. There are many ways to repair a painting, but ­everything must be reversible: retouching will alter in colour at a different rate and over time the repair can grow obvious. The gallery would use a modern adhesive to join the tear, which is easy to use and non-aqueous (water can shrink a canvas). This glue would be applied carefully by hand, with a very fine tool – maybe even a dental pick. The area would be under magnification so the restorer can see this delicate work. Or they might reweave the canvas; the individual threads twisted back together, under microscopic conditions – almost like doing surgery. A suction table [which holds the picture down by creating a vacuum, and controls humidity] could be used if the tear stretched the canvas. This stretch could be "sweated out" on a ­suction table by turning up the humidity. If the paint has crumbled it could be ­re-adhered with Isinglass – fish glue – under a magnifying glass, or a heat-activated ­adhesive. The tear may need support. You could line the whole of the back of the canvas but for such a special painting it's more likely to be patched. A piece of ­synthetic sail cloth would work. To retouch the damaged area we would use a pure pigment in resin form, which is reversible – we can't use oil paints. I have seen worse ­damage than a 6in tear – one man picked up a painting from us, and his child fell right through it. He handed it straight back. I think they may display this Picasso under glass from now on.