We received a maintenance order for the product in this photo, but found tin oxide deposited at the bottom of the pot.

Impurities floated on the solder surface, and tin compounds precipitated to the bottom.

To remove the precipitates, put solder in and heat it up. Then use a flathead screwdriver or similar tool to scrape the bottom of the pot. Precipitates will float to the surface.

Please be careful not to burn yourself with hot solder splashes.