Arhi tried his hand making DIY rosin-based solder flux. He added crushed rosin to isopropyl alcohol until it had the desired viscosity.
The video is a test of the new flux on 1 mm and 0.5 mm pitch components. By his account it works better then some commercial products, but there’s also more smoke and residue.
Via the forum.

Hi
Nice tip on doing flux, i was looking for something so and tried my own experiments but the results weren’t quite… mmmh nice.
Thank U.
been doing that for ages, but i must say, that because of flux made this way i’ve learned that i really need to clean my boards after soldering them – microcontrollers go bananas otherwise. This flux is conductive as hell.
Can you describe where you got the rosin from? Was it in chunks/sold form -or- liquid/dissolved form?
Also was it _really_rosin or was it a synthetic ‘equivalent’ ?
Pictures would be _great_!
Thanks,
rsk.
I experimeted with rat shack Flux using that alcohol from paint stores. Get a paint filter and coffee filter then dump the Flux in. Throw in the alcohol and wait a while. The precipitate will be an amber liquid Flux and in the filter will be WHATEVER that gelling compound is, but white.