"God sends meat and the devil sends cooks." - Thomas Deloney
I like the sunbathing idea but I'd wait until the stones were just about dry before doing it. It's a great way to kill the little guys it just won't penetrate far into the stone.
mikemac: Perhaps I shouldn't have been sounded so final in my judgement on my first post on this thread. Resin in some synthetics may degrade in oxidizing solutions (and in UV light, actually). This is probably pretty slow degradation. Some ceramics (oxides) are somewhat soluble in base (base etches glass, for example). This could change the grit and abrasive characteristics of the stone. This is probably also a pretty slow process. Nevertheless, I've never tried it and different stones are made with different binders, additives, etc. The best advice for the OP is to take a small chunck of his particular stone(s) and soak them and check for any differences. To just throw your stones in some stuff and hope for the best seems foolish to me, is all.
I think the soaking in vinegar or anything else is largely a symbolic gesture. All you have to do is get it totally dry so all the mold dies, from that point on it's just a cosmetic question. A simple flattening should deal with that.
I agree with Craig. A bit of mold won't hurt anything, once it's gone.
If you want to completely dry it out, I don't think the sun is going to harm your stone. What are stones pressure baked at, does anyone know? Some sunlight won't touch that temp, I wouldn't think.
some stones are baked at about 200 degrees C and some around 1300 degrees C ... depending on the stone, they should be fine in sunlight. Some stones, however, dont do well in sunlight because the water evaporating causes cracks in the stones (think chocera). Those kinds of stones do well in a well ventilated cool place out of the sun. I would advise against putting stones in an oven... heating up the water will create steam and can hurt your stone (cause cracks or breakage). Also, resin bonded stones (the ones fired at 200 degrees C) dont do well in solutions with bleach or vinegar. Sintered stones (those fired at the higher temp) do ok, but you want to rinse them well when you're done (maybe soak for a while in fresh water, drain, soak again, etc.). Clay bonded stones (like king) should be alright soaking in a light solution, but no oven.... i've tried... they crack from steam.
Yeah, no oven then.
Really all you need to do is get all the gunk off the outside then leave them somewhere dry for a few days. Sun or other heat sources are just to speed that up, but why risk it? It's not like you need to sharpen every single day, is it?