A degradation of asphalt or coal tar pitch caused by holding it at high temperatures for too long in a closed kettle. This overheating causes the bitumen to break down and lose its softening point, meaning it will melt and flow at lower temperatures than intended once installed on the roof.
Heard on the job
We left the kettle firing during the delay and caused fallback in the asphalt, so we had to pump it out and start fresh.
Insider tip
Fallback permanently ruins the physical properties of the bitumen. You cannot fix it by letting it cool.
Also heard as
- refluxing