This post will save you money, I guarantee it. Early on in my bass playing life, when I had paltry sums to buy strings with, I used to boil them to remove the skin, oil and cack which causes them to go flat. I've always liked zingy (played in, mind) strings - plenty of top end, good mids and rounded lows. I'm not a massive fan of the flat dull thud which some people regard as fine - not my thing, and my opinion mind, don't be offended if you're happiest playing 10 year old strings to get that tone from the 70s ;-)
Boiling worked, I even added washing up liquid at one stage - but, of course, you're effectively promoting chemical reactions. Water acts as a mild acid of sorts, and promotes rust in the steel of the strings - particularly, I noted, in the cores of the strings I was using at the time (rotosound Geddy Lee style PSDs I recall).
More recently, I've used Warwick black labels since the warwicks I have came with them, and they seem like a great compromise between cost, sound and longevity, and I hunted for a better (read: lazier and more effective) way to clean strings.
I can recommend this: the meths does less harm to the strings (they certainly seem to survive better), it actively stops water (we used to add it to petrol tanks to soak up water and improve running in cars with carbs), and it does an excellent job of removing the oils and skin grease from the windings of the roundwounds.
I use an old sweet jar, with extra sealing inside the lid to ensure there's no evaporation. Big neck (you need to get the strings in there), and buy enough meths to fill the jar. I found it in B&Q, available in smallish bottles. Don't worry if it's pricey, the meths will very quickly pay for itself.
All you have to do is wrap the strings up in a small enough loop to get them in the jar, make sure they're under the meths, stick the lid on and leave them for as long as you want. I've left strings in there for months(!) and they've been great.
When drying, make sure you do it somewhere ventilated - the meths will stink the place out while it evaporates from the strings - but it won't take that long.
I can get 3 or even 4 uses out of a set of Warwick black labels: that's a serious saving on a 6-string bass.
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