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Confused by how much and when to put the flux on. I did a little brazing at college and we just dipped the rod in flux as we used it. Some internet sources do this others mix with water and paint on before heating. Just had a go and the rod did not flow but I think I was not quite hot enough ( drak cherry red) but even at that temp the bit of pasty flux I painted on was looking burnt.
35% silver rod.
I always put a little on the joint dry. Then lightly heat the rod and dip it in flux. Flux will burn first. That's sort of the point of it. Just get the metal hot and feed the rod in.
When I was an apprentice we were taught to paint sticks of solder with a flux mixed with water and let dry, but we still used flux (again mixed with water as a thick paste) when soldering.
You're using silver flux? There's no such thing as too much flux - I use paste and liberally coat the joint before brazing. Only time I use powder is sometimes when tacking.
Some fluxes do turn black at normal temperatures.
Flux came with the rods so I hope its correct!. Small trial pack so I could experiment.
So the general consensus is both on rod and joint and don't be stingey!
I shall have another go hopefully some time in the week. Thanks all.
the cleaner the better, paste flux, dip the rod in powder when it's hot. As Ben says, the more the better. put it where you're not brazing to serve as temp indicator as well. it's cheap.