50. How Fluxing Affects Brazing

Good & Bad Tips

Good

Bad

Good tips have an even flow to all four corners.  The flow does not go over the sides or down the front.  The arrow in the left hand picture shows a little bit flowing down the front.  This much is all right but we try to not get any flow over at all.  Place the wire near the back of the tip.

How Much Flux to Use

Removing flux

Flux can be removed with hot water and a little brushing.  The parts can be tumbled in cold water or sandblasted.  Flux can also be removed by brushing.  Flux that is very hard to brush off while hot can sometimes be removed rather easily once it cools.

If you severely overheat the flux it may be very hard to remove.  In this case you need to add more flux and reheat.  The new flux will mix with the old flux and then you can remove it.

Anti Flux – braze stops

There are chemical preparations sold that are applied like paint.  They are designed to stop flux flow at a particular line.  They generally work pretty well.  Experiments can be run using Milk of Magnesia from a drugstore.

Crystallized flux

This happens rarely but when it does happen it is best not to use the flux.  These are the crystals we found in the flux.   I took the flux and just washed it in warm water to separate the crystals.    This is out of new containers.    These are 50x pictures.  The metal rod is a paper clip (.032” dia.) for scale.