I've got a brilliant technique for choosing my next can of shaving foam. Working on the principal that no matter what properties that the manufacturers claim for the product on the can, all shaving foams are fundamentally the same, then I use the reliable indicator of the colour of the cap. That is something that they cannot lie about – it is patent and obvious. So I always try to find a shaving foam which sports an unusual tint to the lid. It makes no difference to my shaving but it does brighten up my bathroom.