[noddytown]

I was having a lemsip in my fav mug which was a bit stained and noticed bits of "stain" floating about in it ha ha . So later I found a tub of out of date lemon juice in the cupboard , and poured in half of it into the mug and swished it around, left it an hour and dipped in a dry dishcloth and a few wipes and presto a clean mug again . So don't ever throw out old lemon juice (citric acid , is it ? )