We use to put them in the cement mixer with a couple of house bricks. Also my mate had a speed boat in the sixties,and we would all tie are new jeans together and and go around Bournemouth bay a few times...(:)
dont bleach them you dont know what the base colour will be, the best way is to take thwe zesty side of a grater and run that doen the centre of each leg. Denim is surprisingly durable, the look will look fashionable not chavtastic at the end.