For a speedy clean up that does great, try about a cup of vinegar and a tablespoon of salt. Put them in a container and shake for a minute. Let it sit about five minutes and shake again. Then rinse off and most will be very shinny just like new. Since I've started doing this, I never tumble pennys. This does better job (shinny) and doesn't waste time. Add more soak time if really cruddy. GL Tom