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My response on the other thread is "At the moment if I want to switch rosin, I clean my bow hair by wiping it on a microfibre cloth until I can't see any more coming off (it takes about 6 swipes). I don't know how well that works."
The only "chemical" I'd risk is baby shampoo. There's a third thread where I relate an anecdote about my teacher using something similar when a student in order to restring her bow less often. She may have used washing up liquid, but baby shampoo might be safer.
No problem with moving the question @Mouse
@Gordon Shumway I doubt if baby shampoo would do anything since rosin is not water soluble.
No, I agree. The problem of cleaning a bow is not one I've faced yet. In addition to the rosin, there will probably be some dirt and dust sticking to it. That may or may not be washable.
I Googled it, and as usual, there are as many opinions as there are violinists! However, the most common answers mentioned using denatured alcohol, not rubbing alcohol. (Rubbing alcohol has an oil in it that will remain on the hairs.) If you have an expensive bow and/or a wood bow, it's best to unscrew the frog to separate the hair from the stick. (Denatured alcohol will eat through the finish on the stick!) Some put the hair in a bowl and let it soak, some use tissues, some use paper towels, and some even use a toothbrush. Once cleaned, it is important to let the strings completely dry, even overnight, before applying the new rosin.
... denatured alcohol... best to unscrew the frog to separate the hair from the stick. ... put the hair in a bowl and let it soak... some even use a toothbrush.
That pretty much covers the method I once used on my good CF bow.
The bowl soaking is more akin to bowl dipping...
... 3-4 rounds of dipping with fresh alcohol for each round.
Give the cleaned bow hair a good shaking and the alcohol will have dried off in just a few minutes. (Again, I did this with a CF bow so no fear of splatters on the stick. I think if/when I do this on a bow with a varnished stick, I'd protect it from splatters with something.)
When done, the dry bow hair was a bit stiff, I'm guessing from dissolved rosin residue. That's where the very soft toothbrush came in.