I've just cleaned my old strings by submerging them in denaturated alcohol. Posting my observations here in case somebody is interested. The strings were the original strings that came with my American Fender Jazz bass, most likely, Fender 45. I used them for around 15 months, so they should have been changed 5 times over. The strings spent around 20 hours in the alcohol. When I put the E sting on, it sounded pretty much like new. But, to my surprise, the very high bright harmonics disappeared within a few minutes. By the time I put A on, the brightness of E was gone. The same happened with the rest of the strings to a lesser extent. Still, overall, the strings sound much better than the ones that I took off, which spent 3 months on the bass. I would say, they sound like new stings after 1 month. That quality seems to persist so far. I have a few theories as to why they became duller in a few minutes. I suspect that wearing out of the strings includes two components - mechanical degradation, e.g. stretching and lost of stiffness, and the grime getting into the string. While cleaning removes the grime, it does not fix the structural/mechanical part. Probably, while the strings were in the box, they sort of returned back to their original form, but once stretched again, they gradually came back into their stretched state, hence lost the brightness vey quickly. Or, maybe, the leftover alcohol made the strings sound brighter. Also, there may still be some grime inside, and as the alcohol evaporates, the viscosity of the grease increases. Now I'm cleaning the strings that I took off. They were not as heavily abused, so I'm curious to see if they will have the same funny de-brightening happening. It would be interesting to hear how much success other people had with this.