I was beginning the follow-up [*] when I thought, maybe we are actually agreeing furiously?
It all started like this:
I wasn't trying to suggest that you should use a dry iron, that's plain silly - yes, you should wet the iron and use the solder on the iron as a heat transfer medium to get the parts hot.
What I was trying to say is that the solder which makes the joint should be applied to the joint, and *not* first to the iron.
That way the solder is cooler than the joint when applied, and it won't melt unless the joint is hot enough, and wet enough, to melt it. Which means it's almost impossible to get a dry joint.
[*] I may post it anyway, lots of lovely math and numbers :) - but that sort of thing takes a while to writebut as this is
Wow, is that indium/bismuth based? Usually I use lead (shhh!) or tin based, but I don't do delicate modelling. Though I used to make bespoke SMT soldering iron bits in the very early SMT days, including ones for soldering directly to chips (by hand), so I can do tiny :)
However you will want to heat the metal up to somewhere, say 30 degrees, above the solder's melting point in order to get good flow etc; call it maybe 200 degrees for the 179 degree stuff, which works out at about a 6 ounce iron for 1mm brass sheet.
Thermal resistance of the iron is supposed to be in the "is about equivalent to 4,000 joules at 50K iron tip differential" bit as above, though I agree it's not clear.
aye, like many things, that it is.
-- Peter F