Answer:
I have cleaned my collection in solution of warm water and Sun oxy clean solution(can get at Walmart - it is their generic of Oxy Clean. I put a half a scoop of solution in a large bowl of warm water and then used a wash cloth to wipe the pieces off. My pieces were dusty prior to cleaning and now are back to their beautiful white porcelain. It did not do any damage to the porcelain either.
MM - from Minneapolis MN 3/2010