Bleach, sodium hypochlorite, will dissolve vulcanite if given enough time. Soaking a pipe stem in a diluted solution can damage it significantly if left for too long. Oxi clean and similar products are sodium percarbonate.... which when activated with water acts like bleach but will not dissolve your stems. This will make restoring stems easier for you. Household bleach is setting you back.
I disagree. I have bleached literally hundreds of stems--never ruined one. Granted if left in the bleach for an extended length of time-days- it might damage your stem.
Oxy-clean,in my experience does little to remove oxidation. As Mike stated above he sometimes needs to bleach the stems AFTER soaking in Oxy-clean.
Pipinho. I get the impression you took your stem out of a soak of some sort(what did you use?) and went straight to the buffer. That AIN"T gonna work. You can if you spend enough time with the right compounds make it shine. It will also have a very wavy surface and most likely some blurred edges,burned button etc.
A LIGHTLY oxidized stem can be buffed without any type of soak or sanding,but if there is heavy oxidation or scratches ,toothmarks etc. it will need to be sanded. Wet sanding works best for me.
I like to start with the finest grit of sandpaper than will give me a nice SMOOTH surface,usually 360 or 400 grit. Sometimes you can start with 600. Care must be taken to avoid rounding the face of the stem. I've found that on most stems only the area close to the button needs to be worked with the courser grits and as you get toward the end(face) of the stem you can usually use finer grits.
It is important that the stem be sanded thoroughly with each grit so that the sanding marks from the previous grit are totally removed.
If you don't want to soak the stem first, you can use the water you're sanding with to check to see if the oxidation is gone. After sanding for a while,rinse the stem and while it is still wet take a close look at it. Any remaining oxidation will show up as brown or greenish colored areas indicationg more work needed in those areas.
I sand up to 800 grit usually,sometimes with some stems (small dainty stems- especially acrylics) I go to 1000 and take it to the buffer and hit it with white diamond. I can usually see my ugly mug in the reflection after buffing with white diamond. For a little added sparkle I hit it with red jewelers rouge and for a little more-wax it with Paragon.Carnuba will do the same but the Paragon seems to hold up longer.
If your bowl is grungy you can scrub it down with Murphy's oil Soap or Simple Green,taking care not to get a lot of water in the bowl or shank. A little water ain't gonna hurt it.A toothbrush can be used to scrub a rusticated pipe. Let it dry overnight before proceeding.
Unless the pipe is beat( talking smooth pipes here) up you can hit it some brown tripoli and then some white diamond,then wax.Buffing a rusticated pipe with a compound can be tricky and can make it look like Sh+T.
Buffing(with a compound) in my opinion should be kept to an absolute minimum,both when restoring and for maintenance.It's kinda like prepping a car for paint. Get it smooth-then buff.
Also keep in mind there are alternative to sanding. Magic erasers will remove light oxidation,so will 0000 steel wool although you can;t get in close to the button with it.There are several way to get a nice shine,but the secret-IMO- is completely removing oxidation and getting the surface smooth-before buffing.