I’d like to chime in with my experience using OxyClean powder that you dissolve in water and create a stem bath. While the results for me are extremely inconsistent, the only thing I can pin it on are different vulcanite compositions?
When this sort of bath works, it works wonderfully. A green stem goes in, and a black or almost black one comes out - without any trace of pitting or roughness, basically in a condition many would be happy with! Personally I sand them further to get them shiny, but by no means is the texture of the vulcanite affected by the process. This is the outcome that looks like magic.
In other cases, what you get is a whitish-green matte surface you do have to sand down to get to the actual rubber. Here is an example - all four stems entered the bath together, all were fairly oxidised but moderately, meaning that you could still see that black rubber was underneath. Two came out perfectly, two came out looking worse than when they came in.
I personally still use it because the time saved on the good ones makes up for the sanding work I have to do on the bad ones.
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