[Luciano] didn’t want to drop a lot of cash into a flux and solder paste applicator so he built his own for about $5. He re-purposed a hot glue gun which you can usually find at a dollar store.

2 Solder balling occurs if the solder paste spatters (small explosive) or the solder paste slump and the flux spreads. 1- 1.5°C/second ramping rate is recommended to minimize those defects.