Here’s what happens with china. As it’s used and it ages, it gets very small cracks in the glaze called crazing. There’s not a lot you can do about a piece that’s already crazed. Dirt, grease and other disgusting things get into the crazing and cause discolouration. The image above is from a planter, so it’s probably dirt. In my pieces, it’s probably grease.
There are a few things that you can do to try and get rid of the stains. My friend Reggie Darling has a long piece about using hydrogen peroxide to remove stains. It’s a lengthy process, involving submerging the piece in hydrogen peroxide (H2O2) for several days and then baking it for a few minutes in an ELECTRIC oven (as gas ovens could cause an explosion!). You can read about the process and Reggie’s results, here. They were dramatic. You can either get lots of smaller bottles of H2O2 at the drug store, or a larger bottle, which is a higher percentage, at a beauty supply store.
Another suggestion is to make a past of a cleanser like Comet®, or something that has some bleach in it, and spread it over the stains. You can leave it overnight and see what it does. Do not use bleach full-strength as that can damage the porcelain.
Since the old tureen I have is already pretty badly damaged, I put some Soft Scrub® on it and left it all day long. The process cleaned the dish up a bit, but some of the stains go all the way through the china.
Other suggestions for cleaning china are denture tablets, water softener with a Z code, and naval jelly, which is terribly caustic. Natural options include a paste of white vinegar and salt, baking soda and water, or a past of Oxyclean® and water.
What are your tips for cleaning china?