Got a dirty coffee maker? Go ahead, admit it. The pot is clean, but the coffee maker is filthy. As a matter of fact, it is so bad, you are positive that one of your neighbors is going to call the dirty-dishes police. Well, fear not. All you need to remove tough coffee stains from glass, metal or plastic is a strong detergent. One purely wonderful detergent we know of is SODIUM CARBONATE. Pure sodium carbonate can be purchased at a swimming-pool supply store. Just look for the bottle marked PH INCREASER or SODA ASH. Mix a teaspoon or two in a cup of warm water. No matter how badly stained your coffee machine might be, it will come clean. And that's the On The House tip for today.