The Musée d'Orsay in Paris, best known for its collection of Impressionist paintings, is hosting an exhibition devoted to Saint-Gobain. That is not as odd as it seems, because the French group is a bit of a museum piece itself. Founded in 1665 by Colbert,Louis XIV's finance minister, it supplied the mirrors for the palace of Versailles. Colbert, setting the pattern for many subsequent finance ministers, rushed to protect his French champion by banning all imports of Venetian glass. By 1688, through the invention of glassware casting, SG cornered the EU market.The company has gone from strength to strength. Yet even Saint-Gobain is nervous that some private equity funds might think of taking a swipe at it. The risks have greatly diminished since its acquisition of BPB, the UK plasterboard group.