I'm a scientist. A very very dirty 50s Charatan consumed all of my alcohol while cleaning yesterday. I made a point to stock up on my pipe cleaning supplies in lab today. A half-liter of pure methanol and a half-liter of isopropanol, each pure 100%.
A chemist will tell you, strictly speaking, that cleaning a pipe is a question of the appropriate solvents. It's all 'chromatography' in a sense, i.e. the leaching of various materials in the appropriate solvent. Tars and gunk (generically speaking) are materials of various molecular weights and solubilities and they leach out to varying degrees in the appropriate solvents.
Smoking from a properly-dried pipe that was cleaned with isopropanol (rubbing alcohol) or methanol (wood alcohol) is less dangerous, and represents less exposure than cleaning a wound with an alcohol (isopropanol) wipe or touching wood alcohol while finishing up a countertop after sanding.
I mentioned earlier: gunk and germs are two different things. I think most of us are cleaning pipes. Nobody I know has ever caught a disease from a pipe, or even a toilet seat for that matter. Nevertheless, appropriately
cleaning a pipe will almost entirely
sanitize that pipe.
I'll close by saying that alcohols are safe for cleaning pipes, and disinfecting them if you're in need of that particular reassurance, however you should be sure that they are properly dried after a few hours, and you should be absolutely sure if you use Ethanol that it does NOT contain the bittering agent denatonium (read the ingredients; if in doubt, don't use). Furthermore these following solvents are not recommended: acetone (unless you're completely stripping your briar; it may damage your stem and remove any paint thereon), chloroform, heptane, hexane, pentane, toluene, or xylene. Pure chemicals marked 1-Propanol and 2-Propanol are acceptable, and in fact 2-Propanol is iso-Propanol. Obviously do not use kerosene or gasoline.
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