When making fused flux, the raw materials are dry mixed together and then melted or fused into a liquid state using a high temperature furnace. Once the melting is complete, the flux is cooled. This can be done by using a stream of water or a large cooling block. After the flux is cooled, it is crushed or ground into particles. Various particle sizes are made to ensure optimal performance in different applications.

Advantages of fused flux include:

Non-hygroscopic flux particles do not absorb water, so any surface moisture can be eliminated by simply drying the particles in a low temperature oven at 300 degrees Fahrenheit.

Low temperature drying of the condensation on the fused flux particles provides better protection against hydrogen cracking.

Flux particles produce chemically consistent welds.

Fused flux particles can be recovered through a flux recovery system without loss of size or composition.

A disadvantage of fused flux is that the high temperatures used in the manufacturing process make it difficult to add alloys and deoxidizers.