use only 40% hydrogen peroxide. This is not the peroxide you buy at the chemist. You need to buy the stronger type that is found at a beauty supply store. Always wear protective gloves to protect your skin and pour into the plastic container. soak the items sometimes for a month, and up to 6 months. I like my items to be completely covered as they soak.
The peroxide loses strength over time. You will know when to replace the peroxide because it tends to get discolored, and starts to have an odor. The brown crazing is usually old grease that has become trapped in the crazing of the glaze. This old grease darkens with age.
If I have a piece of porcelain that is more delicate, and I don’t want it soaking in peroxide for any length of time, I simply wrap the piece in old white rags soaked in peroxide, only putting the wet rags on the spots that need whitening. I place it in a large rubbish bag, and seal it. If using rubbish bag method, the rags will need re-soaking every few days, as they dry out.
Clean your pieces very carefully
Use great care with any cleaning method. It’s a good idea to try the method on an inexpensive piece before attempting to clean valuable pieces. After you have the piece as clean as you can, wash it with soap and warm water to clean off and residue of the peroxide.
NEVER USE CHORINE BLEACH! This will destroy the pottery, porcelain or ceramic piece. It literally eats it from the inside out. It makes the glaze flake of the piece.
Also, please make sure that you carefully look over any piece that you are going to soak. If restoration or repair has been made on a piece of pottery, porcelain or ceramic, chances are the piece will be ruined in this cleaning process. If in doubt ask a specialist in restorations before you try this.
