(More context below. For now, my question is which solvent would work best).

Which solvent would you use to clean your chain(s) during an extended tour? The idea is to carry a small quantity (less than 500 ml / 2 cups) to clean chains once a week.

(1) Flammable solvents (kerosene/diesel) cannot be carried on a plane so I would have to purchase at destination.

(2) Non-flammable (e.g. citrus based) solvents are allowed on planes but may not be worth the trouble if the chain has to be washed in water and allowed dry for an extended period of time before being lubricated. It also seems that some of these non-flammable solvents contain alkalis that may damage metal parts that would be stored in them.

(3) I believe that there are specialized solvents that are very effective and dry fast without leaving residue. They do not seem to be available to mere mortals like me. They also seem to be sold in large quantities (5 gallons, drums). So that may not be an option.

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Two years ago, I was a total newbie. We toured all summer with the kids and the routine involved pouring more oil once a week. Needless to say, at the end of the summer, there was a heavy coat of gunk on the drivetrain, to the point of provoking occasional chainsucks. Chains had to be changed after 3000kms, which I found troublesome, not because of the cost (negligible) but because I didn't like the idea of having to hunt for a replacement chain in the middle of a longer tour. Since then, I wipe. Much better.

Then I tried (aggressively) to learn about chain wear. My understanding is that most of the elongation comes from friction between pins and plates. It has little to do with road dirt and more with the size of the sprockets and chainrings used to power the bike (larger sprockets/rings translate into longer chain life). It also, very probably, has much to do with keeping "the inside" of the chain, i.e. the plate/pin interface, as clean as possible, something that can reasonably be achieved with solvents and mechanical action, such as vigorously shaking the chain in a (wide mouth) bottle, or for the consummate perfectionist, with an ultrasonic cleaner. Anecdotal evidence suggests that chain life can be increased several-fold, almost certainly twice as long, possibly up to 10 times as long.

There are also plenty of contrary advices, but they seem to be aimed at user error. Using solvent may cause more harm than good if it removes factory applied lubricant that is not replaced by new lubricant. This is why solvent has to evaporate completely before the chain is re-lubricated. Hence suggestions to rinse chains in alcohol and finish the drying process in an oven...

i will not take chain cleaning/lubrication to such extremes. But I rotate two chains every 800kms or so (once a week on tour). And at home I've started to shake-in-the-bottle with mineral spirits, allowing the off-bike chain to dry a fews days before re-applying lubricant. Early in the process, but it seems to effectively slow down elongation and the amount of (magnetic) gunk that settles at the bottom of the solvent bottle attests to the fact that wear occurs internally (i.e. the gunk isn't from road dust, but from metal particles generated by the chain flexing around the sprockets).

My commute is short and our winters are long, such that a large proportion of our cycling mileage accrues on tour. Which explains why I am considering cleaning our chains on extended tours, once a week (or actually, carrying the off-the-bike chains in a bottle filled with solvent). As of now, I lean towards stopping at a gas station / supermarket/ hardware store to get a small amount of kerosene (or white gas). Kerosene (white gas) can also be used as fuel for camp stoves. So the logistics would be more straightforward.